Sika deer (Cervus nippon) is an endangered species, which has been listed on the IUCN Red List of Threatened Species and the Appendices of the CITES. In addition, Sika deer is also classified as a Category I key species under the Wild Animal Protection Law in China. Reproductive behaviors of Sichuan sika deer (C.n.sichuanicus), including rutting and copulating, fawning season, circadian rhythms of estrous roar and mounting behavior, etc., were observed and recorded from April to December 2006 and from March to November 2007 in Tiebu Natural Reserve, Zoige County, Sichuan Province, China. The results indicated that Sichuan sika deer was seasonal estrus animal. The behaviors of estrus and copulation were observed from early September to the middle of December, with a higher frequency ((86.99±3.24)%) occurring between October and November. The earliest rutting and mating behaviors occurred at 8 September and the latest in 16 December, covering a period of 90 -100 d (± 6 d, n=90). There was a low positive correlation between the mating date of female deer and their mating experience (Kendall's tau-b and Spearman's rho, 0.3 < r < 0.5, P < 0.05), and the mating date for the adult females were slightly earlier than that for the first breeding ones. The behaviors of estrous roar and mounting in males have noticeable circadian rhythms, in which each have two peak periods (05:00-08:00, 18:00 -21:00) and several low rhythm at night. U-test showed that the roar frequency and mounting rate were significantly different between daytime and night (P < 0.01). The roar behaviors in males were high positive related to their mating behaviors (Kendall's tau-b and Spearman's rho, 0.8 < r < 1.0, P < 0.05), and there were statistically significant differences in the frequency of circadian roar among dominant males, subordinate males and single males (P < 0.01). Hinds fawning took place from the end of April to the end of July, and most frequently ((91.51± 4.96)%) between May and June (P < 0.01). The earliest calving happened on 29 April and the latest on 28 July, covering a period of 80 -90 days d (± 5 d, n=130). There was a low positive correlation between the fawning date of females and their parturition experience (Kendall's tau-b and Spearman's rho, 0.3 < r < 0.5, P < 0.05), and the fawning date in adult females was slightly earlier than the first breeding females. Its litter sizes ranged from one to two fawns once, and single and twinning rate were 98.86% (± 6.96%, n=129) and 1.01% (± 0.07%, n=1), respectively. Among all behaviors, feeding behavior has a largest proportion, followed by the resting and moving behaviors during pregnancy and lactation. The proportion of feeding behavior during lactation lower than it would be during pregnancy, which is related to the different situation of food resources in the two periods. Food resources were relatively scarce in winter (pregnancy period), and rich in summer (suckling period).