We observed velvet antler growth and antler casting in 59 male Père David's deer (Elaphurus davidianus) in Beijing Nanhaizi during August 2013 and 2014, using a telescope (Swarvoski 8×42 WB) and camera (Canon 550D 70×300). The antler casting time of the population tended to be delayed with decreased age, and some dominant and high-ranking bucks cast their antlers earlier than the oldest bucks. We gathered 89 antlers from December 2012 to February 2014 and found that more individuals cast the right antler earlier than the left (48.8% versus 34.1%); the remaining deer (17%) cast both antlers on the same day, and that the same individuals cast the heavier antler earlier than the lighter one(41.5% versus 41.5%). The average time interval between left and right antler casting was 1.98 days. There was a significant negative correlation between antler weight and casting time in 2013 (R²=-0.898, P=0.000, n=32) and 2014 (R²=-0.842, P=0.000, n=57). The antler casting time of the population showed a delayed tendency as antler weight was decreased, but the first antler cast was not the heaviest one. During June 2013 and May 2014, we investigated the start and end date of the antler cycle in nine populations of Père David's deer using field, literature, and telephone surveys. The nine populations were from Beijing Nanhaizi Milu Park (BNMP), Jiangsu Dafeng Milu National Nature Reserve (JDMNR), Hubei Shishou Milu National Nature Reserve (HSMNR), Liaoning Liaoyang Qianshan (LLQ), Zhejiang Linan Milu Conservation Center (ZLMCC), Zhengjiang Cixi National Wetland Park (ZCNWP), Tianjin Qilihai National Wetland Park (TQNWP), Hainan Tropical Wildlife Zoo (HTWZ), and Hebei Luan River National Nature Reserve (HLRNR). We found that wild populations cast earlier than captive and semi-free populations. A tropical population that immigrated into Hainan Province also had a regular annual antler cycle. The start and end dates of the antler cycle differed between years and habitats. The start date of antler casting was not related to altitude, longitude, latitude, annual average temperature, captivity, or climate; rather, photoperiod and hormone status regulated the antler cycle. Other factors affecting the cycle included age, antler weight, nutrition and energy status, population density, and phenological characteristics.