Hydrogen energy is regarded as a promising clean energy source due to its high energy density, environmental friendliness, and wide range of applications. As a key component of alkaline electrolyzers, composite membranes play a crucial role in determining the efficiency and stability of alkaline water electrolysis systems. In this work, composite membranes for alkaline water electrolysis were prepared via an immersion precipitation phase inversion method using Polyphenylene sulfide mesh as the reinforcement layer, polysulfone as the polymer matrix, polyvinylpyrrolidone as the pore-forming additive, and Nano-zirconia particles as the inorganic filler. The effects of polyvinylpyrrolidone content and molecular weight on the microstructure and electrochemical properties of the membranes were systematically investigated by evaluating area resistance, alkali uptake, gas evolution current density, and membrane morphology. The results indicate that the introduction of polyvinylpyrrolidone significantly influences membrane formation, leading to the evolution of the internal structure from a dense morphology to a porous asymmetric structure with sponge-like, finger-like, and mixed pore configurations. Meanwhile, the area resistance of the membranes shows a pronounced dependence on both polyvinylpyrrolidone content and molecular weight, whereas the working current density exhibits relatively weak sensitivity to molecular weight variation. These findings demonstrate that tuning polyvinylpyrrolidone parameters provides an effective strategy for regulating pore structure and improving the performance of composite membranes for alkaline water electrolysis.