Considering the growing demand of edible oils, cultivation of oilseed crops is very important to fulfill the oil requirements of world population. Among oilseeds, safflower is a native plant of Iran and adapted to dry climatic conditions with high potential for oil production.This study was conducted to determine the effects of thermo-priming on 10 genotypes of safflower ( Carthamus tinctorius ). A laboratory and a field experiments were conducted separetly. In the laboratory experiment, germination parameters and in the field experiment morphophenological traits were measured. A factorial experiment according to a completely randomized design was used in which seeds were treated by three levels of temperature (40, 60 and 80 C) in three levels of time (10, 20, and 30 h) and the results were compared with control condition (non-primed seeds).Comparison of three temperature levels revealed that 40 C and 60 C tempretures had higher germination percentage and germination rate and the comparison of three levels of time revealed that 10-hour treatment had greater and positive effect on the percentage of germination. As the temperature was increased more than 60 , more declines was observed in the traits.Also, by comparing the means of three time levels, 10-hour temperature treatment had the highest germination rate. For the farm experiment, seeds of selected genotypes were treated by 60 temperature for 6 or 10 hours and then they were planted in the farm alogside with control seeds (non-primed) in a randomized complete block design and morpho-phenological characters were measured and compared with control conditions. The results showed that seed treatment led to the different results in different genotypes so that in some genotypes, traits means were increased while in the others decreased. In Ac-sterling, days to 50% germination, days to maturity, 1000-seed weight, oil percent, seed yield and seed weight in head were increased due to temperature treatment. Also in C111 genotype, days to maturity, head size, 1000-seed weight, oil percent, seed yield and seed weight per head were higher in temperature treatment compared to the control. In M420, days to maturity, head size and days to 50% flowering was higher in temperature treatment compared to the control conditions. In Kooseh, days to 50% flowering, oil precent and head numbers were higher in plants grown from seeds treated with high temperature compared to the control condition. According to the results of laboratory and the field, seed thermo-priming may enhance germination parameters, but the effect on morpho-phenological traits genotype-temprature-duration-specific. Keywords : safflower, priming, oil seed, germination, morpho-phenological variation