To further study the nondestructive testing technology of line laser scanning IR thermography, the effects of adjustable parameters and tested material parameters on the thermal imaging results was explored to obtain the best defect detection results. COMSOL software was used to establish a finite element analysis model of line laser scanning carbon fiber composite materials, and the maximum surface temperature difference between the defect center and non-defect area was selected as the characteristic quantity to measure the detection effect. The influence of the linear laser length, defect size, and defect depth on the thermal imaging results of carbon fiber reinforced plastics (CFRP) was analyzed, and the relationship between the three and the detection effect was fitted. This study provides a reference for the establishment of a laser scanning thermal imaging detection system and accurate and reliable detection standards.