With the improvement of mechanization, shield machine began to be widely used in the construction of urban rail transit, shield machine digging process will produce a large amount of soil. In order to study the feasibility and adaptability of shield improved slag applied to the assembly metro station fertilizer tank backfill, with the Shenzhen-Huizhou intercity improved shield slag as the research object, through the method of numerical simulation, the use of improved shield slag and C20 concrete backfill effect is compared and analyzed, and the results show that:(1) Strength of 12.5 Mpa, 15 Mpa, 17.5 Mpa improved slag soil for backfill can be basically the same as C20 concrete, which can replace C20 concrete for fertilizer tank backfill.(2) The best effect is achieved by using 12.5 MPa for backfilling. Compared with other working conditions can significantly reduce the maximum Mises stress at the location of the variable section of the roof slab, which has a significant effect on the displacement and stress at nodes 12, 27 and 28, and can significantly reduce it; (3) Using improved shield dregs instead of C20 concrete for fertilizer tank backfilling has certain practical significance for site construction in terms of sustainability benefit and economic benefit. The research results have certain guiding significance for the sustainable utilization of improved shield dregs in related construction.