The heat released from an aluminum-air battery has a great effect on its performance and operating life during the discharge process. A theoretical model was proposed to evaluate the resulting thermal effect, and the generated heat was divided into the following sources: anodic aluminum oxidation reaction, cathodic oxygen reduction reaction, heat production against the battery internal resistance, and hydrogen-evolution reaction. Quantitative analysis was conducted on each part, showing that all heat production sources increased with discharge current density. It should be noted that the heat caused by hydrogen evolution accounted for the most, up to 90%. Furthermore, the regulation strategy for inhibiting hydrogen evolution was developed by addition of hybrid additives to the electrolyte, and the hydrogen-evolution rate was greatly reduced by more than 50% as was the generated heat. This research has important guidance for the thermal effect analysis of aluminum–air batteries, together with control of the thermal management process by inhibiting hydrogen evolution, thus promoting their practical application.