The invention provides a topology structure for improving flexibility of a multi-terminal flexible DC power transmission system. Through changing a connection topology structure of a flexible DC converter station and an AC side, each converter station can be in interconnection with multiple AC regions, when the quantity of the AC regions of the converter station is greater than the quantity of flexible DC converter stations, the multi-terminal flexible DC system can be in interconnection with the multiple AC regions through switching operation of an AC side breaker, and flexibility of multi-terminal flexible DC power transmission is greatly improved. Compared with the prior art, the topology structure is advantaged in that power supply reliability and operation control flexibility of a terminal transformer station are improved, and mutual power support of the multiple AC regions can be realized through multi-terminal flexible DC power transmission.