Mating behavior is a species-specific characteristic of the species’ social structure and mating system. Studying copulation systems can help understand cohesiveness and stability of a primate society. From November 2013 to October 2014, we observed mating behaviors of a semi-provisioned group of Yunnan snub-nosed monkeys (Rhinopithecus bieti) in the Baimaxueshan National Nature Reserve, Yunan, China. All-occurrence and focal animal sampling methods were used to collect data on duration and frequency of pre-copulatory, copulatory, and post-copulatory behaviors of subjects involved. We found that monkeys mated year round, with a reproductive peak during the mating season (roughly from July to September); mating was initiated mainly by the females (76%), females also showed an observable solicitation peak during the mating season. Male mounting frequency (yearly mean= 0.43 times/month, n=5) and rate of ejaculation/mounting (yearly mean 19%, n=5) showed no significant variability. Therefore, the relationship between seasonality and sexual response for mating differs between the sexes. Females ran or jumped into a male's range of vision to come into notice, then prostrated and glanced at the male to solicit being sexually mounted. The distance between a prostrating female and the resident male affected the success rate of the solicitation (<1 m, 68% vs. 2-5 m, 40%). If the first solicitation failed, females might prostrate other several times (max= 4 times) to sexually coax the resident male. Multiple sexual solicitations significantly increased the rate of the resident male’s mounting over that of a single solicitation (79% vs. 52%). After mating, females might groom the male, but this allogrooming was not significantly related with whether the male had ejaculated in this female.