Abstract: In order to study the effect of estrus synchronization on the reproduction rate of Simmental cows by artificial insemination with sexed semen, 1 824 unpregnant healthy cows with moderate body condition, and at the age of 2 to 4 years old, were randomly divided into 3 groups of A, B and C, which were treated with different combinations of Gonadorelin, chloroprostanol sodium, and luteinizing hormone to determine the reproductive performance indicators of cows. The results showed that the estrus rate, conception rate, and parturition rate of cows in group A were the highest, with a significantly higher estrus rate than group B and C（P＜0.05）, and a significantly higher conception rate and parturition rate than group C（P＜0.05）. There was no significant difference in the second natural estrus mating rate among the three groups（P＞0.05）. It could be concluded that a better reproduction rate and financial return could be achieved by following measures: Simmental cows administered with intramuscular injection of Gonadorellin 100 μg on day 0, intramuscular injection of chloroprostal sodium 0.8 mg on day 7, intramuscular injection of 100 μg Gonadorellin on day 9, and were detected for estrus and ovulation on day 10, intramuscular injection of luteinizing hormone（LH） A3 25 μg before insemination.The above measures can promote the estrus rate of cows, improve the effect of artificial insemination and increase the economic benefit of cattle farms.