Abstract:By ETAP software， simulation and analysis is made to the isolated small power grid with photovoltaic.The result shows that though the large capacity motor starting will not cause the power grid instability， the direct starting current is often large，which will cause great impact on the grid.Before the photovoltaic power station is put into operation，it’s advisable to do motor start experiment，go on protection setting according to the measured data or take measures to reduce the motor start voltage drop.