Abstract: Prediction results of productivity of refracturing wells often has large error because the effectiveness failure of the previous fractures in refracturing wells is difficult to evaluate. The validity of previous fractures is fitted according to the pre - fracturing production rate and watercut of refracturing wells. A two - phase 2 - D plane fracture - reservoir mathematical model is built taking into consideration the effects of both previous and new fractures. The productivity of refracturing wells is evaluated through achieving the numerical solution of the model. This evaluation method can more accurately predict the performance of wells after refracturing and guide the determination of fracturing time and prediction of post -fracturing economic benefits.