Although, extended power mode and cross power mode were put to use widely in subway auxiliary power system ,there were some problems such as big volume ,high noise level in these two mode. Furthermore ,it affected the travel experience seriously when the power system was switched to light load mode because of one of the auxiliary inverter failed. In terms of these situations, parallel auxiliary power system was developed. Taking Malaysia Ampang extension line project as an example, an grid-connected control design of auxiliary power system was introduced based on power droop method . The grid-connected control theory and application were shown detailly . The system was proved steady with good current sharing performance, which could fully fulfil the demands of subway vehicles and improved the power supply redundancy and travel experience.