An improved model to predict OH center dot yield in hydrodynamic cavitation for wastewater treatment is developed. Relaxing the chemical equilibrium assumption, the model can estimate the global average OH center dot yield during the whole oscillation cycle of all bubbles by considering radicals diffusion, cavitation event rate, and bubble radius distribution. Reliability of the model is verified by comparing with experimental data from literature in terms of geometric and operating parameters. The results show that the maximum OH center dot yield is achieved at optimal upstream pressure of 3.6x10(5) Pa, while increasing downstream pressure always enhances OH center dot yield. Decreasing the hole and pipe diameters benefits the OH center dot yield. Finally, a relevant correlation is developed for the design of cavitation reactors.