DC high speed switch (HSS) is the key equipment in multi-terminal DC transmission system. The power transmission capability and operation flexibility of multi-terminal DC system could be affected by the performance parameters of HSS. In order to develop ±800 kV HSS products with better performance parameters, this paper proposes the problems to be solved in long term DC withstand performance, small DC current breaking and DC arc withstand performance. In this paper, the 1 224 kV/1h wet withstand insulation capacity of the prototype is realized by combining the internal and external insulation simulation optimization and insulation verification of the prototype. Through the magnetohydrodynamic simulation of small current interruption, the temperature and pressure distribution in the arc extinguish chamber when HSS interrupts small DC current is obtained. A small DC breaking experimental prototype is trial produced, and the maximum breaking current of the prototype experiment reaches 350 A under 1 kV recovery voltage. Through the magnetohydrodynamic simulation of long duration arcing, the temperature and pressure distribution in the arc chamber during the 4 000 A DC current breaking process are obtained. The research in this paper lays a solid foundation for the development of ± 800 kV HSS products with better performance parameters, and is of great significance for improving the power continuity and the safe and stable operation of multi-terminal DC transmission systems.