The tunnel boring machine would induce ground instability and water and sand inrush when breaking through launching and receiving gate between main tunnel and connection gallery. A new type of sealing device for launching and receiving of tunnel boring machine for connection gallery with mechanical excavation method is designed and developed based on analysis on conventional construction method for connection gallery and boring principle of EPB boring machine. A composite mechanical model of torsional shear and axial tension and a strength check model of key parameters are established. The mechanical properties of the sealing device are analyzed by ANSYS simulation platform, and the device is applied to a connection gallery project in Ningbo. The study results show that: (1) The theoretical simulation provides a reference for reasonable selection of the outer diameter and wall thickness of steel sleeve. (2) The structural equivalent stress of designed sealing device is mostly below 100 MPa, which meets the construction load requirements such as strength and stiffness. (3) The establishment of pressure in a sealing device for the launching and receiving of tunnel boring machine to stabilize the excavation face has a positive effect on actual construction. (4) The application of sealing device in launching and receiving of tunnel boring machine in connection gallery with mechanical excavation method can effectively shorten the construction schedule, improve the safety and reliability and provide reference for similar engineering design and construction in the future.