Application of drip irrigation systems is appropriate for newly planted trees; besides that, there are enough references for designing irrigation systems. But there is not comprehensive information for designing and implementing of drip irrigation systems for mature trees which were previously irrigated by surface irrigation system. In this regard, a research was conducted to investigate the effects of changing surface irrigation system to trickle irrigation system on the growth indices of mature olive trees. The field experiment was located in olive garden of Isfahan University of Technology. Experimental treatments were arranged in a complex factorial design with three replications so that each replication consisted of three trees. The experimental treatments consisted of two dripper layouts (single lateral and loop), two irrigation frequency managements (2 and 5 days interval) and three wetted areas (PW) (33, 45 and 67 percent ). The 33, 45 and 67% wetted area were made by 3 drippers (D3), 5 drippers (D5) and 8 drippers (D8), respectively. An automatic drip irrigation system was used to implement treatments. In this study, surface irrigation with 5 days irrigation interval was considered as control treatment. To determine the spacing of drippers the wetted pattern caused by drippers were investigated in field condition. So that an experiment was performed consisted of three irrigation times (T), (4, 8 and 12 hr of water application referred to as T4, T8 and T12, respectively) and three rates of dripper discharge (q), (2, 4 and 8 l/h referred to as q2, q4 and q8) with three replications. To investigate the pattern of root development within 30 cm of tree, fresh weight, dry weight and fresh volume of roots were measured. During the growing season, the plant indices included the length of annual shoots, the number of annual shoot branches and tree height so that shoot length and the number of branches were measured and recorded monthly. The results of wetted pattern showed that the maximum and minimum of wetted width were 159.8 cm for T12q8 and 63.5 cm for T4q2 treatment, respectively. A linear model with two independent variables as a function of irrigation time and the rate of dripper discharge was developed to predict wetted width in sandy loam soil with high percent of gravel. The evaluation of developed models for wetted width showed that among six evaluated models only one had enough accuracy for predicting wetted width in sandy loam soil with high gravel. The results also indicated that the percent of fresh weight in depths of 0-20, 0-40, 0-60 and 0-80 cm in soil profile was 33, 76, 92, and 100 percent, respectively in surface irrigation system. The percent of fresh weight in above mentioned depths was and 40, 80, 99, and 100 percent, respectively in drip irrigation system in second year. The distribution of the percentage of fresh weight withi 20, 40, 60, 80, 100, and 120 cm from tree trunk was 15, 36, 54, 71, 86, and 100 percent, respectively for surface irrigation system and 17, 36, 53, 69, 85, and 100 percent, respectively for drip irrigation in second year. In single lateral drip irrigation there was no significant difference between irrigation interval and the PW on the indices of fruit and growth. Fruit indices had five percent higher performance in F5 than F2 and shoot length and the number of branches had higher performance in F2 than F5 with the difference of 20 and 30 percent, respectively. The comparison between wetted areas showed that D5 with 25 percent difference in fruit volume had better performance compared with D3 and D8 treatments.In loop drip layout the maximum performance of fruit and growth indices were observed in F2D5 and F5D5 treatments , respectively. The comparison of single lateral and loop drip layouts for mature olive trees which were previously irrigated by surface irrigation system showed that growth and fruit indices were higher in loop drip layout than single lateral layout. Overall, results showed that there was no significant difference between linear and loop drip layout. Five drippers which wets an area equal to 45% of shaded area was recognized the best wetted area and 5-day irrigation interval was better compared with 2-day irrigation interval. The results represented that a combination of 5 drippers with 45 percent wetted area and 5-day irrigation interval was the best combination for mature olive trees in sandy loam soil with 42-71% gravel. Totally, consideration of the type of previous irrigation management, investigation of root development pattern, measurement of the width of wetted pattern caused by dripper, selection of suitable irrigation interval and development of desirable wetting area are the executive solutions for changing surface irrigation system to drip irrigation system in mature trees.