Reproductive performance is an important factor which can affect milk production and improving it, leads to access enough heifers to be replaced within dairy herds. This study was carried out to study conception rate based on the first inseminations and also dystocia. Estimation of genetic parameters were considered using linear model, threshold model, and Bayesian method, by including/excluding random environmental effect. For studying these traits, the data of 83692 Holstein cows, including 203193 individual records, from 41 herds was used which was gathered during 2002 to 2016. The factors affecting on conception rate based on the first insemination were herd-year- season of calving, parity, pregnancy period, and age at first calving were considered. For dystocia, herd-year and season of calving, parity, sex and weight of the calves were studied. Genetic parameters were estimated using linear methods (REML), threshold methods (GLMM) and Bayesian methods based on Gi sampling. Also genetic and phenotypic trends between 1997- 2014 were plotted for dystocia and conception rate at first service. In this study the effects of herd-year and season of calving, parity, pregnancy period, age at first calving, birth type, and calf weight were significant for conception rate. Besides, the effects of herd-year and season of calving, parity, pregnancy period, age at first calving, birth type and calf weight were significant for dystocia. The estimated heritabilities of conception rate at first service, by Bayesian method, threshold method and linear method, were 0.05, 0.04, and 0.02, respectively. These estimates for dystocia were 0.2, 0.2, and 0.4, respectively. According to the variances and standard error estimated for the studied traits, threshold model was more accurate related to the others, and also the reduced model according to “AIC information criterion” it can be suggested as the best model. These results showed that environment factors significantly affect the studied traits. Therefore, improving the management systems can have an important role at changing in operation of these traits.Also according to the results, threshold model and Bayesian model are more precisely methods in studing dystocia and success in the first insemination, Therefore, considering these traits by threshold model in comparison with linear model could leads to in response to selection.