Abstract: The paper aims to clarify distribution regular pattern, variation trend and reason of changing of sunshine hours in growing season in Qinghai plateau. Based on general meteorological data recorded by 43 stations, the author analyzed variation trend and changing reasons of sunshine hours in growing season over the past 50 years in the whole region and 4 different ecological functional areas. The results showed that sunshine hours in growing season decreased significantly in the whole region and Qaidam Basin and the variation was not significant in the other 3 functional areas. Sunshine hours decreased from northwest to southeast on the spatial distribution, and the variation trend differed greatly. The mutation of sunshine hours was in 2004 and 1999 in the whole region and Qaidam Basin, while the mutation time of the other three areas was in 2006 to 2008. The main impact factor of sunshine hours in growing season was cloudiness, and the secondary factors were slightly different. The sunshine hours were decreasing with the increase of longitude and altitude, and decreasing with the decrease of latitude, the influence of longitude was the largest.