Based on winter wheat and summer corn growth regularities in Henan Province and application experiences in optimal irrigation techniques for winter wheat, as well as observed soil moisture data for winter wheat and summer corn from 1994 to 2000, a computer model of soil water prediction and optimal irrigation of winter wheat and summer corn was set up according to the soil water balance equation. The model results were verified by the observed data from wheat fields in Zhengzhou in 1998 and 1999. The relative errors of soil moisture for the next 10, 20, 30 days are -7.3% to 7.7%, -8.3% to 6.8%,-7.6% to 7.7%, respectively. It indicates that soil water can be predicted in one month ahead accurately with this model. Some irrigation suggestions with respect to different wheat and corn growth phases are given, aiming to obtain the maximum yield and the optimal economic benefits.