Guangdong power grid，the largest received power grid of the five provincial grids in Southern power grid，receives power from other regions through AC/DC hybrid networks，thus its security and stability is seriously threatened by faults in both AC and DC power systems.Regional grid interconnection has significant impacts on the transient stability of the original grid.Based on the power flow scheme and main power system network proposed by the mid-and long-term plan of Southern power grid，the paper presents a simulation study on influences of three regional grid interconnection schemes on transient stability of Guangdong power grid.The results show that Guangdong-Guangxi synchronization power grid，in which the receiving grid is interconnected by AC networks and operates asynchronously with the sending grid，can mostly enhance the transient stability of Guangdong power grid.