Abstract: Modern reproductive biotechnologies are important to improve the utilization rate of high quality sheep,shorten the production cycle,accelerate the good breed sheep propagation and promote the development of the sheep industry.These technologies are very complicated technical systems.Taking the technology of embryo transfer as an example,a series of influencing factors,such as individual and genetic differences of donors and receptors,physiological and reproductive conditions,environmental and nutritional status,superovulation scheme,drugs and the skill levels of operators,may affect its entire process and efficacy.In this study,the female Dorper sheep were used as donors to investigate the effects of different operators,selection of stud rams and times of embryo flushing on embryo production efficiency.The results showed that the average number of recovered embryos and available embryos obtained by different trained operators were 3.73 and 3.17 respectively,and there were no significant differences in both of these two indicators between different operators(P>0.05).The times of surgical embryo flushing of the donor sheep exhibited significant effect on embryo production efficiency:when the surgeries exceeded 4 times,the average number of recovered embryos and available embryos were significantly reduced(P<0.05).In addition,the selection of different stud rams also had significant effect on embryo production efficiency(P<0.05):4.11 available embryos were obtained from stud ram 317 and only 3.88 available embryos were obtained from stud ram D1402.