The impacts of climate change on spring wheat yield is studied by using experimental data of spring wheat of typical semi-arid regions on Loess Plateau in 1986─2013, with the combination of meteorological observing data gained from meteorological stations in experimental regions in 1958─2013. It provide the scientific basis for coping climate change. Results showed that, there is a declining trend on precipitation in experimental regions in 1958─2013; the climate tendency rate is -10.966 mm/10 a; annual fluctuation of precipitation is large and the variation coefficient is 20.3%. Precipitation has a declining trend from March to June, which is the main growth period for spring wheat, the variation coefficient of precipitation during March and June is 33.2%. The temperature in experimental region has a very obvious ascending trend and the climate tendency rate is 0.378 ℃/10 a. The aridity index of spring wheat is also showing an ascending trend. After the 90s of twentieth century, the warming and drying character was becoming obvious. Spring wheat yield in experimental regions had an extremely obvious negative relation with the temperature in last ten days of May and first ten days of June(r=-0.492, P<0.01). Higher temperature leads to a higher velocity of blossom differentiation, useful blossom decrease and useless blossom increase, maturing rate decrease and all these caused the decrease in spring wheat yields. The yields of spring wheat in experimental regions have an obvious positive relation with its seasonal precipitation(r=0.306, P<0.05), which demonstrate that the lack of precipitation during spring wheat's whole growing period in semi-arid regions of Loess Plateau is the main factor which influence the yields, a decrease in precipitation caused the decrease of yields of spring wheat. Meanwhile, the yields of spring wheat are extremely sensitive to the changes of precipitation during the middle ten days and late ten days in May, this time period is water critical period for the blossom to start differentiation to the formation of pollen in tetrad of metrocyte, it is a period which is critical for the water supply of spring wheat, so the decrease of precipitation will result in a sterile ovule and blossom, and finally the obvious decrease of maturing rate and yields. Precipitation is the key climatic factor of the yields forming while increasing in temperature is the main restriction factor of the yields forming of spring wheat. Understand the background of climate warming and drying in semi-arid regions on Loess Plateau, the yield of spring wheat have a declining tendency; negative effect of climatic factors on the growth and yields forming of spring wheat is increasing and the uncertainty of yields increased.