The integration of distributed generation(DG) into the distribution network may incur the falseprotection action by inverse-time over-current protection.The DG impact on short-circuit current in the distribution system is analyzed,and the formula of short-circuit current under various conditions are deduced,then the possibility offalse action by inverse-time over-current protection is analyzed.A 10 kV distribution system with DG is used to calculate the starting current and time characteristics of inverse-time over-current protection,and simulate the short-circuit current and the action time,as well as the false actionpossibility of inverse-time over-current protection.The results show that the possibility of the false action is high with location between the fault point and the DG when the short-circuit occur in the DG's upstream.