Based on the runoff data at Mujiaqiao hydrological station of Yanggong River basin and the meteorological data of Lijiang city during the period 1979 - 2016,this study analyzed the variation of the runoff and its main influencing factors. The results showed that the discharge of the Yanggong River basin exhibited an increasing trend and then decreasing trend during the study period. Though the discharge increased during 1980s,1990s and 2000 - 2009,the discharge decreased during 2010 - 2016. The discharge during 2010 - 2016 decreased by 42% (0. 88 *10~8 m~3) compared with the average discharge of 2000 - 2009. Moreover,the correlation analysis showed that precipitation and temperature were the main control factors for the Yanggong River runoff. The influence of precipitation on discharge mainly occurred in rainy season whereas the influence of temperature on discharge mainly occurred in melting season. The variation of snow and ice meltwater caused by the rising temperature resulted in the different change of runoff and precipitation.