The bearing capacity of pile foundation is closely related to the soil layer around the pile and the bearing layer under the pile end, and the selection on the bearing layer directly affects the length of the pile. The selection of a reasonable bearing layer is of certain significance to save the project cost and reduce the environmental impact. A hospital complex building project is taken as an example to analyze and compare the bearing capacity and economy of cast-in-place piles under different bearing layers. The results show that the post-grouting technology can improve the bearing capacity of a single pile and reduce the pile length, so as to save the project cost and reduce carbon emissions. The results can provide some reference for similar projects.