Based on the theory of risk analysis, using the data related to water demand and supply of winter wheat in recent 40 years in North China, the risk probabilities of the different water demand and supply rates for non-irrigation or under conditions of irrigation for 1～5 times with the amount of 675 m/hm² every time during the whole growing period of winter wheat were estimated. The results show that the risk probabilities of different water demand and supply rates take on decreasing tendency from north to south in North China, which exhibits decreasing tendency from middle part to inshore, from middle part to west in south and central of North China. Making the risk probability≥90% of the water demand and supply rate≥70% and the risk probability≥75% of the water demand and supply rate≥80% during the whole growing period of winter wheat as main indexes, the proper complementary times of irrigation based on risk analysis during the whole growing period of winter wheat in different districts are ascertained. If 1～4 times of water supplement can be implemented in North China, the water demand guaranteeing high and steady yield of winter wheat can be satisfied. In some districts which is suitable to irrigate for 3～4 times, there are 5～6 times of irrigation in traditional ways which is severely superfluous. If 1～2 times of irrigation can be reduced, it is feasible to save water by 675～1350 m³/hm².