Abstract: For the structural characteristics of the "radar + infrared" composite stealth system and the magnetization characteristics of the radar absorbing coating, the magnetic thickness measurement model for the radar absorbing coating in a composite stealth coating is established and the thickness measurement algorithm analyzed. It is found that when the sum of the thicknesses of the infrared coating and a certain primer in the composite stealth system is much smaller than the thickness of the air coating, the magnetic thickness measurement can ignore the influence of the thicknesses of the infrared coating and the primer, and that the thickness of the radar absorbing coating can be directly measured by using the electromagnetic characteristic relationship that the magnetic force is proportional to the thickness of the radar absorbing coating. Besides, a magnetic thickness measurement sensor is designed and the magnetic force measurement test is carried out. The results show that the magnetic thickness measurement system has a simple structure and accurate measurement results.