Abstract: With the development of electricity spot market in China, market mechanisms have brought more and more influence on the existing power system operation and dispatch modes. For winter heating provinces in northern China, the electricity spot market trading mechanisms bring great challenges to ensure the safe operation of power system and the heating mode of cogeneration units. In order to solve this problem, this paper analyzed the clearing situation and existing problems of northern electricity spot market during winter heating periods, and proposed a novel electricity spot market mechanism based on thermoelectric decoupling mode. The declaration systems and assessment methods of cogeneration units were established in this paper. The proposed mechanism in this paper could not only simultaneously guarantee the heating and electricity supply of large-scale cogeneration units, but also alleviate excessive heating declaration of power generation side, which could promote full competition of various generating units and the consumption of new energy under electricity spot market mechanisms. The necessity and effectiveness of the mechanism proposed in this paper could be proved by the case of the actual pilot province system in electricity spot market.