[Objective] The research aimed to study the variation characteristics of pan evaporation and its influence factors in Qinghai Lake basin during 1961-2007.[Method] By using the climate tendency rate method,the variation characteristics of small pan evaporation(20 cm) and its influence factors in Qinghai Lake basin during 1961-2007 were analyzed.[Result] In recent 47 years,the pan evaporation in Qinghai Lake basin presented the decreasing trend,and the tendency rate was-47.75 mm/10a.Except in autumn,the pan e...