Due to the impact of heat stress on reproductive traits in dairy cattle, this study was conducted to estimate the genetic components of the conception rate and nonreturn rate of dairy cattle under heat stress conditions in Isfahan province. The data was used from the VAHDAT cooperative breeders and General Directorate of State Meteorological in Isfahan from 1990 to 2013. After editing and preparing the data and computing the Temperature-Humidity index, 34305 records of 21405 cows were studied. Conception rate was defined as number of inseminations per conception and nonreturne rate in 45 and 90 days after first insemination, were considered within 15 to 45 days and 90 days respectively. Nonreturne rate is a binary trait that is measured at a certain time after the first insemination. Thus, if the animal does not need to re-inseminate thuring this time, 1 and otherwise 0 was coded. Significantly of the effects on the reproductive traits was evaluated using proc Genmod in the statistical software SAS (9.1). Genetic components were estimated based on animal model and random regression methods using AIREML and Bayse. Direct heritability of the reproductive trait were closed to 0.035 and for heat resistance 0.004. The selection for production traits can reduce the thermal resistance in animals. Traits in this study included conception rate and nonreturne rate showed a decreasing trend with an increase in THI. The results indicated that with increasing temperature humidity index, the genetic variance of heat resistance wase increased. The genetic differences were observed between the animals for resistance to heat stress. It can be concluded that genetic selection of animals to resistance heat stress is important for the future. Genetic variance for heat resistance in conception rate, nonreturne rate in 45 and 90 were (0.006±0.0034), (0.00008±0.0001) and (0.0001±0.0001) respectively. Due to the large variance for conception rate, recommended that should be used conception rate for genetic evaluation in heat stress conditions. Keywords : Heat stress, conception rate, nonreturne rate, random regression