Abstract: Based on the evaporation of Erhai Lake from 1962 to 2008 and the observation data in Dali weather station, evaporation variation and related direct climatic factors influencing evaporation were analyzed. The results indicate that evaporation from Erhai Lake takes on the decreasing trend with climatic warming, and the relationship between water surface evaporation and air temperature is not significant. Evaporation from Erhai Lake decreases with the increase of total cloud cover and relative humidity, and it increases with the increase of mean wind speed and sunshine duration. The main reason causing the decrease of evaporation from Erhai Lake is the increase of total cloud cover.