To investigate the effects of translucence of glass-fiber reinforced plastic (GFRP) on flash infrared thermography nondestructive testing,optical properties of GFRP laminates were quantitatively measured and studied,and it is found that GFRP laminates have obvious translucence.According to the measuring results,absorptance and full-absorption thickness of GFRP laminates were calculated.Translucence model and conventional model for delaminate defects and debonding defects were compared and analyzed.The simulated results show that translucence may reduce signal?intensity of defects and change its change rule,which will lead to missing detection.