As a key efficient transportation equipment in oil-gas extraction, vane-type multiphase pumps face significant performance limitations due to extensive vortex formation in flow channels. This study systematically investigates strong-weak vortex evolution in impellers using vorticity decomposition, secondary flow diagnosis, and rigid vorticity vector analysis. It examines how inlet gas volume fraction and flow rate affect axial vortices, circumferential vortices, and pressure pulsation. Key findings include: 1) Tip leakage vortex (TLV) in these pumps demonstrates fracture zones, leading to a proposed “front-middle-rear leakage vortex” structure; 2) TLV diffusion and shedding represent strong-weak vortex transitions, with mutual compression between front and middle vortices directly causing fracture; 3) Blade geometry correlates with fluid potential rotor enthalpy evolution to predict vortex patterns; 4) Circumferential vortex intensity increases with gas accumulation, while rapid axial vortex development influences gas distribution. Time-frequency analysis shows gas phase presence amplifies pressure pulsation and low-frequency disturbances in TLV regions, with axial vortex proliferation being the primary contributor to enhanced pulsation intensity. High-flow conditions intensify peripheral pulsations through unbroken TLV, while reduced front leakage vortex and rear vortex shedding attenuate pressure fluctuations.