An inverter grid-connected system applied to feed an alternating current electric power to a three-phase alternating current electric grid, the inverter grid-connected system including: an inverter module converting a direct current electric power into the alternating current electric power; a switching module coupled between the inverter module and the three-phase alternating current electric grid, the switching module including a first switch, a second switch, a third switch, a fourth switch, a fifth switch and a sixth switch, the first switch connected to the second switch in series to form a first route, the third switch connected to the fourth switch in series to form a second route, the fifth switch connected to the sixth switch in series to form a third route; and a controller electrically connected to the switching module to control the switching module, so that the alternating current electric power is fed to the three-phase alternating current electric grid, characterized in that wherein the controller firstly turns on the first route, and then the controller turns on the second route if the third switch and the fourth switch in the second route meet a first specific condition, wherein the first specific condition is that a voltage level of a side of the inverter module connected to the second route is equal to a voltage level of a side of the three-phase alternating current electric grid connected to the second route, and then the controller turns on the third route if the fifth switch and the sixth switch in the third route meet a second specific condition, wherein the second specific condition is that a voltage level of a side of the inverter module connected to the third route is equal to a voltage level of a side of the three-phase alternating current electric grid connected to the third route. an inverter module converting a direct current electric power into the alternating current electric power; a switching module coupled between the inverter module and the three-phase alternating current electric grid, the switching module including a first switch, a second switch, a third switch, a fourth switch, a fifth switch and a sixth switch, the first switch connected to the second switch in series to form a first route, the third switch connected to the fourth switch in series to form a second route, the fifth switch connected to the sixth switch in series to form a third route; and a controller electrically connected to the switching module to control the switching module, so that the alternating current electric power is fed to the three-phase alternating current electric grid, characterized in that wherein the controller firstly turns on the first route, and then the controller turns on the second route if the third switch and the fourth switch in the second route meet a first specific condition, wherein the first specific condition is that a voltage level of a side of the inverter module connected to the second route is equal to a voltage level of a side of the three-phase alternating current electric grid connected to the second route, and then the controller turns on the third route if the fifth switch and the sixth switch in the third route meet a second specific condition, wherein the second specific condition is that a voltage level of a side of the inverter module connected to the third route is equal to a voltage level of a side of the three-phase alternating current electric grid connected to the third route.