Abstract: An assessment model for effects of climate abnormity on wheat production in North China Plain(WHTMOD)was built．WHTMOD consists of wheat phonology simulation model，photosynthesis simulation model，yield formation simulation model，water balance model，and nitrogen dynamic mode1．The physiological processes such as crop photosynthesis，respiration，and distribution of biomass among organs in wheat are considered in the model，and the effects of temperature，daylength， C0₂，water， and nitrogen are also considered． WHTMOD can be used tO simulate the wheat growth，development and yield formation，and to express the effects of climate abnormity on wheat prod uction for studied areas．Validation of model shows that there is a good agreement between the simulated and observed values．