In order to study the circannual rhythm of reproductive characteristics in Pére David's deer (Elaphurus davidianus) and its adaptability to the environment, the casted antler were collected during three annual winters (from December to February) of 2014 to 2016 in Beijing Milu Ecological Research Center (BMERC), Beijing, China. Then harem masters were observed and recorded during the rut time (from May to September) of 2015 to 2017. Offspring date of birth during the offspring period (from March to July) from 2016 to 2018 were also recorded. Combined with the environmental factors from 2014 to 2018 such as annual mean temperature, seasonal mean temperature, monthly mean temperature, annual precipitation, start and end of rainy season, and population density, we studied circannual rhythms in antler casting, harem master alternation, calves birth of Pére David's deer and their environmental influencing factors. The results showed that: (1) there were annual differences in the circannual rhythms antler casting, harem master alternation, calves birth of Pére David's deer. (2) Antler casting date started in December, ended in late January or early February. (3) There was a second estrus period in Pére David's deer population. The estrus period started in late May or early June, and ended in early September. The estrus duration from 2015 to 2017 were 91d, 102d, and 110d respectively, which had a tendency to prolong. (4) The offspring period started in mid-March or mid-April, and ended in late May or late July. (5) There was synchronization relationship among circannual rhythms in antler casting, harem master alternation, calves birth. Antler casting start date, median antler casting date, antler casting end date, rut start date, rut median date, offspring start date, median calving date and offspring end date were synchronization advanced than last year respectively. (6) The circannual rhythms in harem master alternation did not show the phenomenon of advance or delay with the increase or decrease of the annual mean temperature, season mean temperature or monthly mean temperature, while circannual rhythms in antler casting increased with the mean temperature in December, and offspring start date, median calving date increased with the mean temperature in September of the previous year. (7) The circannual rhythm in calves birth did not show a corresponding synchronous change with the precipitation factors. While circannual rhythms in antler casting showed advancement with the increase of annual precipitation. Rut start date and rut median date appeared to advance with the increase of annual precipitation in the previous year. (8) There was no synchronization advanced or delayed of circannual rhythms in antler casting, harem master alternation, calves birth as the population when the density increased or decreased. The circannual rhythm of the reproductive characteristics of Pére David's deer was a complex process, affected by the environmental factors such as climate, nutrition, population density, and latitude.