Abstract: Based on a lot of experiments on farm field, the effect of moisture coerce on growing and yield of cotton were analyzed. The experimental result showed that the most sensitive period of moisture of cotton is bud period, the cotton being in moisture coerce during the flower and bud period would make the cotton yield decrease a lot. Using the models of dated water production function that are most popular in internationality, the suitable cotton model of water production function in Hebei region was obtained.