With the expansions of the scale of HVDC transmission from west to east in the Southern China Power Grid (CSG) and the increase of the transmission power in Yunnan Power Grid, the coupling between the AC and DC stability control systems becomes deeper and the ability of regulation and control turns to be weakened, which further worsen the high-frequency problem of Yunnan Power Grid. Hence, a multi-DC coordinated stability control system is designed and implemented. It reduces the risk of water abandonment and supports the safe and stable operation of CSG by sharing the associated power sources amang HVDCs. In addition, in order to verify the multi-DC coordination stability control system, Xindong HVDC bipolar block field test is planned and implemented. The field test results verify that the stability control strategy is correct, and the devices acted reliably. At last, further improvements of the proposed system are also prospected.