As a new generation of DC transmission technology，voltage source converter based high voltage direct current（VSC-HVDC）system is being developed and applied worldwide.The engineering technology，engineering application and future development for VSC-HVDC are summarized and analyzed，respectively.A comprehensive technical analysis is made of VSC-HVDC including main circuit design，converter topology，control and protection system，VSC-HVDC cable，converter valve testing etc.to point out the technical barriers and future development directions.This paper also gives an overview of the application and status quo of VSC-HVDC projects in the world.With an eye to the characteristics and demands of future grid development，the engineering application trend of VSC-HVDC projects is demonstrated，which shows that the VSC-HVDC technology has a critical role to play in future grid development.