HVDC Light is a new technology of DC transmission, in which VSC(Voltage Source Converter)acted as the core. Control system adopts the PWM (Pulse Width Debugging) technique to reach the high controllable DC transmission. Firstly, the basic structure and fundamental principle of the HVDC Light system were introduced briefly. Then, a simulation model for the typical three-level HVDC Light power transmission system was built on MATLAB. The simulation results were analyzed at last. The simulation results show that the HVDC Light system has good stabilization accuracy and response speed. This study provides a theoretical basis for further research on the physical model of the HVDC Light system.