There are two operating modes in micro-grid，that is grid-connected mode and island mode，The smooth switching is an important measure to ensure the secure and reliable operation of micro-grid.In this paper, considering micro-grid operating modes of smooth switching from two sides,
on the one hand is a system-level micro-grid overall control strategy, used an integrated control from the combination of using the main control and peer control,on the other hand is a local micro-power control strategy,proposed a improved coefficient droop control ,the droop coefficient can dynamic change with frequency and voltage,At the same time to achieve micro-grid islanded operation mode smooth switch to grid-connected operation mode designed pre-synchronous controller.Finally, MATLAB simulations show that this method can not only realize the process of switching voltage and frequency stability, but also to reduce the number of micro-switch mode power supply control,to some extent reduces the possibility of failure of the control mode switching, improved the reliability of the micro-grid operation.