Abstract: When distributed new energy generators are widely connected to distribution networks in multi-voltage levels, the power flow may be bi-directional during a day and the protection will receive a great impact. The distributed generators(DG) have a positive effect on the short-circuit current and such effect is positively related to the capacity of DGs. As a result of that, the penetration of DGs will be less likely to increase when it comes to relatively high level. In this paper, an optimal configuration scheme for DGs which includes the constraint condition of protection will be introduced. It takes the total penetration of DGs and transmission losses as optimization goals and it’s realized by Genetic algorithm. This method has been tested by simulation of actual networks, and it turns out to be effective