The hydraulic fracture skin effect is an important parameter affecting the production of fractured reservoirs, which is commonly analyzed by the formula proposed by Cinco-Ley.To understand hydraulic fracture skin factor correctly, the imperfection of Cinco-Ley’s formula was proposed by theoretical study on its deduction and a new formula about hydraulic fracture skin factor was established.The new formula is compatible with the skin factor of radial flow and represents the real physical essence of skin factor of hydraulic fractures,indicating the fracture skin factor is independent of fracture length.Hydraulic fracture skin factor can be reduced by enhancing the gel breaking rate or minimizing the fluid-loss distance rather than increasing the fracture length.