Compared with residential restrooms, public toilets usually have higher utilization rates. How to ensure the air quality in the toilets through reasonable ventilation is of great significance to human health. In this study, an office building with a public toilet is selected as the research object, and the Airpak 3.0 software is adopted to simulate the airflow velocity distribution in the toilet with different air change rates and exhaust vent heights. Variations of the air velocity distribution, ammonia concentration, ventilation efficiency, and other parameters, are compared and analyzed. The results show that increasing the air change rate could reduce the concentration of pollutants in the toilet, but it has negative effects on ventilation efficiency. After comprehensive analysis, the desirable air change rate is chosen with the value of 15h-1. The exhaust outlet is set near the source of pollution to facilitate the discharge of pollutants. This work may provide a theoretical basis for amelioration of the toilet ventilation environment.