DC de-icing technology is one of the main methods to prevent ice coating on transmission lines. The two star-connected cascaded STATCOMs connected by neutral point can realize DC de-icing and dynamic reactive power compensation. This paper firstly introduces the operating principle of DC de-icing device, then studies the design of three-phase voltage source rectifier (VSR) control system. To solve the problem of limiting DC de-icing current value under traditional control method, this paper proposes equalization control and saturation modulation control method。Finally, a real-time simulation platform based on NI and RT-LAB is built to simulate. Results show that the de-icing current value is significantly improved, and the correctness of the scheme is verified.