The invention discloses a system testing method of power grid distributed stability control devices. A test command computer performs simulation computation of voltage and current data of each fault surface in a fault scene in real time, thereby forming a test scheme. The test command computer issues the test scheme to each test device through a wireless public network, and each test device adopts a GPS clock synchronization technology to synchronously output voltage and current signals of the fault scene to tested stability control devices, and simulates the power grid operation fault scene, thereby realizing interworking of all links of a master station, substations, execution stations and a communication system of the distributed stability control system in a fault processing process to perform system testing. After testing is finished, each test device reports action information of the tested distributed stability control devices to the command computer, the command computer collects action information of the stability control device of each station, automatically checks a stability control device control strategy, and verifies whether execution logic of the distributed stability control devices is correct.