To validate the feasibility of the construction technology of mechanized construction for wastewater pump room in shield tunnel and the reliability of the bottom sealing concrete of the pump room, an indoor test is designed to simulate and validate the safety of the bottom sealing concrete slab in the high water pressure deep stratum environment. Then, threedimensional(3D) finite difference software FLAC3D is employed to build a 3D numerical model to simulate the bottom sealing situation. The FLAC3D internal contact element is used to simulate the contact surface between the bottom sealing concrete and the outer shield body, and further examine the influence of considering the contact on the calculation results of the model. The results show the following: (1) The design of simulation system is reasonable, the test results of mechanized construction of pump room bottom sealing test in main shield tunnel can meet the expected requirements, and the mechanized bottom sealing grouting can meet the design requirements, indicating the feasibility of the technology. (2) The contact surface has a great influence on the calculation results of the model, resulting in a better prediction of the force of the contact surface. (3) Generally, the underground water pressure in the actual project is far lower than the test one, the results of the indoor test and numerical simulation have a certain safety reserve, and the sealing technology of the mechanized construction of pump room is feasible in the actual project.