Voltage Source Converter (VSC) based High Voltage Direct Current (HVDC) technology is a newly deve- loped power transmission technology. The basic principle and structure of multi-terminal VSC-HVDC is introduced and its steady-state mathematical model is set up. An improved power flow algorithm is deduced, which not only decouple the relationship between AC and DC systems’ variables in the strict mathematical form, but also can be integrated with the conventional power flow program and exhibit good accuracy and convergence characteristics compared to conventional technique. A numerical example of IEEE 14-bus test system with a 3-terminal VSC-HVDC network is given. The results show that the proposed steady-state model of multi-terminal VSC-HVDC and corresponding power flow algorithm are correct and effective.