Abstract: This paper summarizes the possible reasons of wind speed decreased in China for the last 50 years. Most studies pointed out the observed wind speed in China decreased obviously by about (0.10~0.18m/s)/10a for the last 50 years. The possible reasons came from both natural (internal climate system) changes and anthropogenic effects. The former includes both of the winter and summer East Asian monsoons weakened, the South China Sea summer monsoon intensity weakened, the South Asian summer monsoon reduced, the frequencies of cold waves and dust storms over China decreased, and frequencies of extratropical cyclones over East Asia declined. The latter refers to urbanization, the changes of land use, the global warming caused by anthropogenic emissions, and the effects of wind farms. The reasons causing the wind speed decline are very complicated in China for the last 50 years, further research is needed to explore a quantitative estimation on the mechanisms and key factors.