Abstract: In order to reveal the effect of the tip clearance on the cavitation characteristics in the main flow passage of the helical axial multiphase pump, this paper uses the Zwart-Gerber-Belamri cavitation model based on the Rayleigh-Plesset equation, and uses the SST k-ω turbulence model in different cavitation stages. The cavitation characteristics in the main flow passage of the helical axial multiphase pump are studied, and the cavitation in the main flow passage of the helical axial multiphase pump is more accurately revealed by considering the tip clearance. The results show that at the tip of the blade, in addition to the low pressure area and cavitation in the flow passage, there are also low pressure areas and cavitation distribution on the suction surface of the blade. In the critical cavitation stage, there is a weak cavitation distribution in the gap between the impeller inlet and the blade inlet tip clearance; with the development of cavitation, to the fracture cavitation stage, the cavitation distribution area moves from the blade pressure surface to the blade suction surface. It shows that the tip clearance has a great influence on the cavitation performance in the main flow passage of the helical axial multiphase pump. The research results can provide a engineering reference for the improvement of the cavitation performance of the helical axial multiphase pump.