This paper firstly reveals the problem of centralized multi-infeed HVDC being connected into Guangdong and Guangxi power grid at present, then aiming at Wudongde multi-terminal UHVDC transmission project which will be put into operation in 2020,compares and analyzes the stability of Guangdong and Guangxi Power Grid when LCC or VSC is used at inverter side of Wudongde DC transmission project from three aspects including multi-infeed effective short circuit ratio(MIESCR), the risk of commutation failure of DC projects caused by AC system faults, and the influence of AC faults on the stability of receiving-end grid. Research results show that using VSC converter at receiving-end of Wudongde UHVDC will not decrease the MIESCE of each DC project in Guangdong and Guangxi Power Grid, and will enhance the ability of withstanding severe AC system faults significantly.