Static Synchronous Compensator (STATCOM) is a kind of parallel reactive power compensation equipment in FACTS system. To study the reactive power regulation of STATCOM in microgrid, the relationship between reactive power flow and voltage in microgrid is analyzed theoretically in this paper. The direct current control is used to control the reactive power exchange between the microgrid and distribution network based on a given reference voltage. Then the simulation research on reactive power flow control of a microgrid system connected STATCOM is carried out. The simulation results show that the voltage at PCC point will be unstable under the two conditions. STATCOM can effectively maintain the voltage balance of PCC point in the microgrid access to the grid and meet the requirements of flexible regulation and stable operation of microgrid.