Due to the complexity of shale reservoir geology, hydraulic and micro-fractures can be coupled into an extremely complex symmetrical or asymmetrical fracture network around vertically fractured wells (VFW) after fracturing. The important and useful work is to analyze the transient pressure response of the VFW, to more accurately predict the productivity of VFW. In this paper, a numerical method to accurately simulate the complex fracture network geometry and analyze the transient pressure responses of the VFW, due to the complexity of the fracture network geometry. The results show a longer fracture length on one side causes a smaller pressure depletion, a shorter bilinear flow, and a deeper and longer the degree of "dip". The more fractures on one side can lead to a greater degree of "dip" and a smaller pressure depletion. With the fracture conductivity on the right side increases, while that in other side remains constant value, it results in a shorter bilinear flow, a deeper and longer the degree of "dip", a smaller pressure depletion, and a weaker bi-radial flow (BRF). In addition, it is found that flow regimes affected by magnitude of fracture networks are mainly bi-linear flow (BLF), "dip" and BRF. The pressure behaviors between asymmetrical fracture networks and symmetrical fracture networks are mainly in the periods of BLF, "dip", and BRF. Through analyzing the transient pressure responses of the VFW, the parameters of the complex fracture network can be well predicted, so that the productivity of the VFW can be estimated more accurately.