Because of extreme weather conditions and the limitation of the transmission power,the DC current can not meet the requirement of de-icing.And it will lead to the formation of the DC transmission line icing,affecting the stability of the UHVDC system seriously.Combined with the de-icing function in Jiuquan-Hunan UHVDC project,the main connection topological structure and characteristics of the round resistance ice mode and hybrid de-icing mode for the UHVDC project is described in this paper,and then the strategy of bipolar synchronous tripping in round resistance ice mode and the modified scheme of UHVDC control and protection function in hybrid de-icing mode are proposed.At last,the feasibility and effectiveness of the de-icing function are verified by RTDS closed loop real-time digital simulation.Reference is provided for the design of UHVDC control and protection system for the de-icing operation mode.