The real-time forecast of irrigation is one of the essential part of the work for compiling a dynamic plan of irrigation water use. It plays an important role in saving water, increasing crop yields and economic benefits in an irrigation area. The real-time forecast of water requirements of crops is the essential and difficult part in the real-time foreast of irrigation. The methods and models for the conventional forecast of crop water requirement ,applied both in China and the world, are based on the application of the historic data from typical hydro-logic years. They can not used for the real-time forecast. In this paper, on the basis of the analyses of the relationship between the crop water requirements and the meteorological factors and non-meteorological factors such as the factors of plant and soil, the method and models for the real-time forecast of crop water requirements based on the factors of weather types, leaves cover percentage and effective soil moisture are presented and recommended. The concrete steps and computer block diagram are introduced. The main improvements are that the weather type is used instead of such four meteorological factors in Modified Peman's Eguation as air temperature, humidity, sunshine hour and wind speed,the leaves cover percentage is used instead of the leaves area index, and an improved equation for calculating soil moisture correction coefficient is proposed. Based on the results of the real-time forecast of crop water requirement and precipitation, the real-time measurement of soil moisture (for dry food crops fields) or depth of water layer (for paddy fields) and the maximum and minimum values of soil moisture content or water depth for getting high yields and saving water, and the calculation of field water balance, the method and models of real-time irrigation forecast including the real-time forecast of the date and quota of irrigation for both dry food crops fields and paddy fields are presented. In this paper, the precision of the real-time forecast and its effects on increasing yield and saving water are also introduced and discussed.