Abstract: In order to solve the problem of large error in predicting the maximum water inflow of roof by using the area analogy method of working face, based on the theory of fluid mechanics, this paper establishes an ideal water inrush model of pipe for calculating the water inflow of roof of working face. Based on the theory of practical ground pressure control, this paper deduces the non-linear formula for the prediction of roof water inflow when the first fracture of transfer rock beam occurs, and reveals the positive correlation between the roof water inflow and the working face inclination width and the first fracture step of the transfer rock beam. Case application proofs that the result of the maximum water inflow in the mining face predicted by water inflow when the first fracture of transfer rock beam occur both mined working face and mining working face, and maximum water inflow of mined working face is more accurate than that predicted by area analogy.