Most of the low permeability reservoirs are tight and shale reservoirs，with small pore，fine throat and high filtration resistance. During the fracturing fluid flowback process，a great quantity of the fracturing fluid is retained in the layer，which causes the low fluid flowback. The mathematical model of fracturing fluid flowback was built based on the microscopic percolation of the capillary bundle model to study the influencing factors of fracturing fluid flowback in different diameter capillaries. Core test was done for natural cores in Fan 154 block of Shengli oilfield to research four influencing factors on flowback rate，including core permeability，oil viscosity，flowback pressure difference and interfacial tension between oil and fracturing fluid filtrate. The results show that the core permeability has greater influence on the flowback rate. When the permeability decreases from 1.276×10-3 μm2 to 0.13×10-3 μm2，the flowback rate declines by nearly 20%. When the oil viscosity decreases from 6.459 mPa?s to 1.192 mPa?s，the flowback rate increases by nearly 15%，and the flowback rate has the same increment when the interfacial tension between oil and fracturing fluid filtrate decreases from 14.617 mN/m to 0.021 mN/m. The flowback rate increases with the flowback pressure difference. But when it is higher than 8 MPa，the flowback pressure difference has smaller effect on the flowback rate.