The thermal environment of the power cabin and high-temperature exhaust gas seriously affect the performance and survivability of the armored vehicle on the battlefield. In order to improve the hostile thermal environment of the enclosed power cabin and inhibit the infrared characteristics of exhaust gas, this paper puts forward a multistage connected ventilation cooling structure based on the unique structural characteristics of the armored vehicle. The structure utilizes the rotating action of the fans to introduce the cold air into the power cabin, volute, and smoke exhaust pipe in turn. The effects of the multistage connected structure on the temperature field and exhaust infrared detection power of the armored vehicle were studied by numerical simulation. It was indicated that the multistage connected ventilation cooling structure can effectively improve the thermal environment of the armored vehicle cabin by about 15.18% and reduce the infrared detection power of exhaust gas by about 11.35%. This paper is of great significance for studying the cooling of the power cabin and the design of armored vehicle’s infrared stealth.