Abstract: Fracture volume of fracturing fractures is an important parameter for evaluating fracturing effect.The commonly used micro-seismic fracture monitoring cannot distinguish effective and invalid fracture micro-seismic points, and the analytical model is not applicable to complex fractures, and the fracture volume evaluated by these methods has a low correlation with fracturing productivity. Therefore, the effective fracture volume calculation model is established by using the dynamic data at the initial stage of fracture backflow. By transforming the dynamic data of the initial flowback stage of fracturing wells, the quasi-stable flow stage was found out and the linear relationship was fitted. The material balance time period of the flowback stage was determined. Combined with the comprehensive compressibility of fracturing fractures, an effective fracture volume calculation model was established. The effective fracture volume of 10 vertical wells and horizontal wells was calculated by this model. The calculation results show that the effective fracture volume is positively correlated with the fracturing productivity, and the correlation is above 0.9, The established method can accurately evaluate the effective fracture volume and predict the fracturing productivity. The parameters required by this method are easy to obtain and accurate to evaluate, which can be used as a new method for effective fracture volume evaluation of fracturing wells.