Abstract: In order to study the distribution and movement of the gas-phase inside blade pumps, the computational fluid dynamics methods were used to simulate the flow inside a blade pump under the condition of gas-liquid two-phase flow, which was verified by experiments. The gas-liquid two-phase flow in the pump was numerically calculated based on the MUSIG model. The Prince-Blanch model and Luo-Svendson model were used to describe the process of bubble coalescence and breakup. The numerical simulation revealed the bubble distribution of different sizes, average bubble diameter distribution and pressure distribution. The results show that with the increase of inlet gas volume fraction, the low-pressure area near the suction side of blade gradually increases. The gas volume fraction increases in the gas accumulation area and wake area near the suction side of blade, and the high gas volume fraction area expands. The average diameter of bubbles in the pump increases. When the inlet gas vo-lume fraction reaches 3%, the gas volume fraction in the larger area on the suction side of the blade is more than 80%, and the gas volume fraction in the near wall area of the volute is less than 1%. Large diameter bubbles are mainly found in the gas accumulation area near the suction side of blade, while small diameter bubbles are mainly found in the wake area, near wall area of the volute and volute outlet section. There is a region with larger average bubble diameter in the flow channel near the suction side of blade.