Abstract: With the continuous inflow of distributed generation, the traditional single-power radiation network becomes a two-terminal or even multi-terminal network which will change power flow and short-circuit current distribution to affect reliability and sensitivity of the relay protection device based on quick-break and over-current principle and the coordinate of upper and lower line protection device. Firstly, Distributed PV systems and the concrete distribution network simulation model were established using DIgSILENT in this paper, then the influence of different location access to power gird and different PV systems capacity on short circuit current and line protection of distribution network were quantitatively analyzed. In the end, different solutions and strategies were proposed to solve the problem.