Abstract: After oil wells fracturing, process of fracturing fluid flowback always exists, and the back flow of proppant during this process is a major factor in evaluating fracturing performance, so it is necessary to study the relative problem. According to the mass conservation law and Bernoulli’s equation, a calculation model of flow velocity at any vertical section inside the fracture is established with considering the dynamic variation of the fracture width and filtration of fracturing fluid during flowback. The critical condition of proppant backflow is after mechanic analyzing of proppant during the process of back flow, and then a reasonable system backflow plan of controlling the proppant backflow is proposed. According to the established model, a reasonable flowback procedure which can control the back flow of proppant in terms of Well Nenping 1 Jilin oilfield is designed.