The use of piezo-catalysis for H2 production from water at ambient conditions has recently gained significant attention, yet the importance of cocatalyst engineering has been largely overlooked. In this study, AuPt alloy nanoparticles were used as cocatalysts on the piezoelectric material BiOCl for H2 evolution driven by sonication. The Au:Pt ratio of 3:1 significantly enhanced the reaction, resulting in a doubling of H2 production compared to Au alone and a tripling compared to Pt alone. Experiments and simulations showed that AuPt alloys promote H* adsorption and facilitate the separation of piezoelectric carriers. Additionally, the cocatalysts enhance the piezo-catalytic reaction by increasing the stress and deformation of the BiOCl microplates. Unlike the photocatalytic process, the piezo-catalytic H2 evolution on BiOCl succeeded due to the suppression of BiOCl reduction by the periodically accumulated piezo-electrons and holes. This research highlights the critical role of cocatalyst engineering in optimizing piezo-catalytic H2 production and presents a promising strategy for efficient H2 generation.