The combustion of multi-hole pyrophoric activated metal belongs to solid combustion and the combustion mechanism is quite complex, which is a difficult problem to be solved. Once the pyrophoric activated metal contacting with oxygen, the oxygen diffuses to the interior of the activated metal within plenty of holes and reacts with it, which enlarges the contact area with oxygen. Consequently, the whole combustion is serious and the temperature rises rapidly. To study the combustion mechanism of chaff, surface heat balance equation is established in this work by taking Mg as the activated metal. To solve this equation, the chaff adiabatic wall temperature distribution is computed by computational fluid dynamics (CFD) in the presence of high speed airflow. Then, chaff surface temperature distribution is obtained by solving the heat balance equations. Finally, numerical and experimental results via infrared (IR) thermal imager are compared to demonstrate the effectiveness of the established equation.