Abstract: In order to ensure the long-term efficient and stable operation of the commutator of the sampling system and prevent the leakage of radioactive materials, relevant study is carried out on the mechanical seal structure of the commutator of the sampling system. From the analysis of the technical scheme and the working principle of commutation, to the study and design of the mechanical seal structure in combination with the needs of the project, and then to the test and verification, and finally a commutator that meets the requirements of the project was developed. In the design of the core sealing structure of the commutator, the bellows sealing structure is adopted to adapt to the relative rotation of the commutator pipe and the inlet pipeline; The bearing adopts double row angular contact ball bearing, which can withstand the radial load and the axial load acting in both directions. At the same time, a small flange with a gap of 0.1 mm is reserved between the bellows seat and the pipe to prevent fatigue of the bellows during the process of rotation and commutation. The air tightness of each pipeline docking cell before and after the test is stable, and the leakage rate within 15 min is less than 10%; During the test, under the 21 L volume, the pressure drop of about 1 kPa in 30min met the requirements of gas sealing, and the study results have been applied in the sampling system of nuclear chemical engineering projects, and positive feedback has been obtained.