Abstract: The influencing factors of birds captured at night were investigated by light trapping at Jinshan Yakou （23º57' N, 101º30'E) of Ailao Mountain, Xinping County, Yunnan Province from 5th September to 5th November 2007 and from 3rd September to 7th November 2008. The influencing factors were analyzed by using hygrothermograph and qualitative analysis. Geography conditions had a great effect on the bird species captured at night. Weather was also an important factor influencing the number and species of birds captured at night. Statistical analysis showed that wind direction, wind force, fog and lunar phase had a significant effect on the species and number of birds captured at night（P<0.01）. However, the effect of wind direction was more obvious than that of wind force. More birds and species were captured during nights with a southwestern wind, fog, crescent moon and old moon. In addition to light is a necessary condition for trapping. But temperature and humidity had no significant effect on the number and species of birds captured at night.