Aiming　at　locating　those　typical　defects　possibly　existing　in　large　scale　wind　turbine　blade　materials,　this　article　established　an　axial　symmetrical　non-steady　state　heat　conduction　model,　which　described　how　to　test　air　holes　inside　the　wind　turbine　blades　using　pulse　infrared　imaging,　and　got　the　temperature　field　and　heatflux　field　of　any　time　during　pulse　heating-cooling　stage,　as　well　as　the　surface　temperature　and　temperature　differences　between　defective　area　and　sound　area　by　ANSYS　simulation　calculation.　From　theoretical　calculation,　the　author　also　reveal　the　mechanism　of　inner　defects　test　by　infrared　imaging,　which　also　validate　the　feasibility　of　NDT　of　inner　defects　by　using　infrared　imaging.