Abstract: The difficulty of optimal clearing model in spot electricity market is the security constrained unit commitment (SCUC) model considering security constraints. Building a good SCUC model to improve the solving speed has been a research focus for a long time. With the continuous development of provincial power systems and the operation of domestic provincial power spot market, the spot market has a more prominent demand for solving the clearing model. In this paper, the research history of unit commitment model is reviewed in detail, and the unit operation model with enhanced modeling of unit operation output constraint, upper output limit constraint and climbing constraint is further proposed. Based on the application of graph theory in linear optimal power flow calculation, the circulating current power flow calculation model of transmission network is constructed and the SCUC model is introduced. Next, a set of electricity spot market clearing model that can further improve the solving efficiency is constructed. Finally, the calculation and analysis of several large-scale examples show that the proposed model can effectively improve the solution efficiency without losing the solution accuracy, and it has more obvious advantages for complex large-scale systems.