Volumeter fracturing technology with slick water as the main fracturing fluid has been widely used in the large-scale development of shale oil and tight oil. Slick water volumeter fracturing has the advantages of complex fracture formation and large reconstruction volume, but narrow fracture width and weak sand carrying performance, and proppant backflow sand production seriously affects the normal production of oil and gas Wells during fracturing flowback and initial production. In order to solve the problem of insufficient understanding of proppant reflux law, this paper established a proppant reflux model near wellbore fractures according to the flowback conditions of shale oil and tight oil. The numerical simulation of proppant reflux during the flowback process was carried out by CFD-DEM method, and the influence of factors such as flowback velocity and closing stress on proppant reflux was investigated. The results show that the order of importance of influencing factors is: flow rate of reflux fluid > closing stress > particle modulus strength > viscosity of fracturing fluid. Under normal conditions, 3 × 10–5 m/s is the critical return velocity of proppant. When the ratio of fracture size to particle diameter reaches 2.5 or below, the proppant is stable. The closing stress/particle modulus values were between 0.001 and 0.002, and the proppant placement maintained a relatively stable state. This understanding has important guiding significance for flowback control, proppant particle size and parameter selection in tight reservoir fracturing.