The crop model World Food Studies (WOFOST) was tuned and validated with meteorological as well as winter wheat growth and yield data at 24 stations in 5 provinces of North China from 1997 to 2003.The parameterization obtained by the tuning was then used to model the impacts of climate change on winter wheat growth for all stations using long-term weather data from 1950 to 2000. Two simulations were made, one with all meteorological data (rainfed) and the other without water stress (potential). The results indicate that the flowering and maturity dates occurred 3.3 and 3 days earlier in the 1990s than that in the 1960s due to a 0.65℃ temperature increase. The simulated rainfed yields show that the average drought induced yields (potential minus rainfed yields) have decreased by 9.7% over the last 50 years. This is to be compared with a 0.02% decrease in yield if the precipitation limit is lifted. Although the precipitation during the growing season has decreased over the last 50 years, the drought effects on the rainfed yields remained to be practically unchanged as the spring precipitation did not decrease markedly.