The invention relates to a virtual current testing device and a testing method thereof for a high-voltage DC circuit breaker. The virtual current testing device comprises a host computer and a virtual current generating device. The two ends of the virtual current generating device are respectively connected with the host computer and a control protection system of the high-voltage DC circuit breaker. According to the testing method, the host computer is configured to simulate various faults of the high-voltage DC circuit breaker, and the current variation conditions of a DC bus, a main branch, a transfer branch circuit and a bleeder branch. After that, the variation information of the fault current is transmitted to the virtual current generating device through the Ethernet by the host computer, and then the virtual current generating device simulates the current variation during the occurrence of a real fault. Moreover, the current information is transmitted to the control system of the high-voltage DC circuit breaker through optical fibers. According to the technical scheme of the invention, the control and protection logic design of the DC circuit breaker can be rapidly and flexibly tested.