Since　the　photovoltaic　power　generation,　wind　power　and　other　distributed　power　supply　are　volatile　and　random,　they　will　affect　the　stability　of　the　grid　frequency.　In　order　to　improve　the　voltage　and　frequency　in　micro-grid,　the　virtual　synchronous　generator　control　strategy　is　proposed　for　inverter　control,　which　can　emulate　the　behavior　of　synchronous　generator,　decrease　rate　of　change　of　frequency　and　provide　dynamic　power　support　to　grid.　However,　when　virtual　synchronous　generators　based　micro-grids　switch　from　islanded　mode　to　grid-connected　mode,　inrush　current　may　deteriorate　the　power　quality　of　micro-grids　and　damage　the　device　in　micro-grids.　This　paper　discusses　the　problem　of　pre-synchronization　and　presents　a　new　pre-synchronization　method　for　grid-connection　of　virtual　synchronous　generators　based　micro-grids.　Accordingly,　parameter　matching　between　virtual　inertia　and　capacity　among　virtual　synchronous　generators　is　analyzed　in　detail.　Simulation　results　show　the　validation　of　the　proposed　method.