Abstract: The H-beam composite support system (PASS) has the advantages of recyclable, high-strength connection, prestressing force applicable and high reliability, so it has been used more and more widely in China. The H-beam composite support system (PASS) used in the foundation pit of the house construction has many vertical support structures and cannot meet the earth excavation requirements of the subway foundation pit well. A standard station foundation pit (about 20 m in width) commonly used in subway engineering is taken as an example. Through comparison and analysis of calculation, the cross-section type of H-shaped steel composite internal support with large span and large spacing is designed. Compared with traditional steel pipe supports, it has a large bearing capacity, large support spacing, The cross-section form is economical and reasonable, and can well adapt to the requirements of narrow and long foundation pits of metro. It has the value of promotion and application.