The temperature difference of the submarine’s wake on the sea surface is the base for the IR detection. In this paper, the temperature difference on the sea surface caused by the submarine’s propellers and the submarine’s hull is studied by solving the three dimensional N-S equations. The results show that under the condition of sea temperature surroundings of minus gradient, such as in summer the upper water’s temperature is higher than the lower water, it is cold wake on the sea surface and hot wake on the submarine’s plane. The temperature difference between the wake and the water around in the wake’s initial part becomes more and more obvious as the wake’s distance gets longer. Through the IR camera, the submarine’s propeller wake is studied under the same temperature status. Obvious IR temperature difference signals can be observed and it is consistent with the numerical simulation for the submarine. The temperature difference of the submarine’s wake on the sea surface is the base for the IR detection. In this paper, the temperature difference on the sea surface caused by the submarine’s propellers and the submarine’s hull is studied by solving the three-dimensional NS equations. results show that under the condition of sea temperature surroundings of minus gradient, such as as in summer the upper water’s temperature is higher than the lower water, it is cold wake on the sea surface and hot wake on the submarine’s plane. The temperature difference between the wake and the water around in the wake’s initial part becomes more and more obvious as the wake’s distance gets longer. Through the IR camera, the submarine’s propeller wake is studied under the same temperature status. Obvious IR temperature difference signals can be observed and it is consistent with the numerical simulation for the submarine.