Water is one of the most important resources for human demands and due to fresh water scarcity, its efficient consumption is one the most important challenges in present century. In agriculture, efficient use of water and modern irrigation methods is required. Two management methods, including regulated deficit irrigation (RDI) and partial root zone drying (PRD), increase the water use efficiency. The aim of this study was to evaluate the effect of deficit irrigation by PRD method on the growth of mature olive trees and to evaluate irrigation water use efficiency (IWUE) of PRD and RDI methods. Treatments of the experiment were consisted of three levels of deficit irrigation levels and three deficit irrigation management and the study was conducted using a factorial randomized complete block design with three replications, and each replication was consisted of three trees, for two years. Irrigation treatments were 100, 75 and 50% of the crop evapotrairation (ETc) (S 1 , S 2 and S 3 respectively), and irrigation management levels consisted of three levels, including regular deficit irrigation )M 1 ( and two irrigation management by PRD, including switching over wet and dry every 9 days (M 2 ) and every 18 days (M 3 ) with irrigation applied once is three days. The olive tree evapotrairation (ETc) was calculated using meteorological data, the FAO Penman-Monteith equation and olive crop coefficient. - Annual shoot length, number of annual shoot branches, and leaf relative water content were measured in growing period, and at the end of the growing period, the fruit index was measured. The effect of irrigation management and stress levels on the growth factor was significant at 5 and 1% levels, respectively. PRD management significantly reduced growth branches compared to regular deficit irrigation. Increment of water stress level and air temperature reduced the leaf relative water content. Relative water content in PRD management was significantly more than normal irrigation. Effect of different levels of water stress on yield, fresh weight, dry weight and fruit volume, and on the average diameter of the geometric and arithmetic was significant. There was significant difference in yield, fresh weight, dry weight, fruit volume, and average diameter of the geometric and arithmetic between all irrigation managements. The M3 increased fruit yield as much as 32 % compared to M1. The maximum and the minimum yield per tree was 11.355 and 4.583 for treatments M 3 S 1 and M 1 S 3 , respectively. The maximum and the minimum of IWUE were 1.53 kg/m 3 and 0.95 kg/m 3 for treatments M 3 S 2 and M 1 S 1 , respectively. The IWUE values in management strategies of M 2 and M 3 increased 22 and 26%, respectively compared to M 1 management strategy. Therefore, Partial root zone drying management increased IWUE compared to regular deficit irrigation. Overall regular deficit irrigation management and 0.5 ETc level of irrigation (supply 50% of evapotrairation) for olive tree to maintain landscape, and partial root zone drying management at 0.75 ETc level of irrigation for economic production (supply 75% of evapotrairation) is recommend. Keywords : deficit irrigation, partial root zone drying, olive yield, irrigation water use efficiency.