Abstract: There is an important effect of crop development on yield formation. Development is the time pointer in the crop growth model. However, the current crop development model of cumulative temperature can not explain the phenomenon of different sowing date but same maturity. At the same time, how the soil moisture affects the crop development is not very clear and the majority of crop growth model does not consider this. In the paper, summer maize in north China was taken as the object to study the stability of several crop development models, effects of continuous temperature and soil moisture on development and its simulation method. The results showed that the stability of the heat units (THU) model was the highest in accumulated temperature (TSUM), developmental unit (CHU) and THU models. Summer maize development process was not only determined by the cumulative temperature or heat units, but also affected by the average temperature in a development phase. The completion of the development process needed more accumulated temperature while the average temperature was higher. A maize development model was established the base on this. This model obviously improved simulation of development process of summer maize, which sowed in different days. There was a significant effect of soil moisture on summer maize development. Increase of soil moisture would cause development acceleration of summer maize in vegetative growth stage. Thus, the tasseling stage would advance. The model based on this could better simulate summer maize development in regional scale.