It will bring a lot of impacts when grid-connected distributed photovoltaic generation on distribution system. Aimed at the practical problems, through the theoretical derivation, the voltage and power losses of PV power generation systems access to the grid is studied according to two factors including different access locations, different access capacity.The voltage profile improvement index and active power losses improvement index are adopted to evaluate the PV influence on the system voltage and power losses. Simulation is carried out on the practical grid, The results show the change law of voltage and active power losses when accessing locations，output of PV system are changed, it provides a theoretical basis of choosing the location and capacity of PV generation system in the actual distribution network