Abstract: Stainless steel cowl in leading edge, front spar and back fillet of rotor blade in helicopter were tested and researched with infrared thermography testing system. By active heat stimulating with heat resource outside, interior different material makes different temperature field in surface of rotor blade, so infrared images could show clearly structure character and damage inside of rotor blade under lacquer coating. Testing results indicated that active infrared thermography test technology could be used to faster inspect damages such as delamination, adhesive failure and corrosion inside composites in helicopter, and it had wide applied prospect in maintenance of daily and emergency for helicopter in service.