Nylon 66 and nylon 6 enhance tire structural strength, durability and stability. As synthetic fiber cords, they have excellent wear resistance, tensile strength and corrosion resistance, occupying an important position in tire manufacturing. Different tires use different cords, so a simple method is needed for rapid differentiation between nylon 6 and nylon 66. This paper compares methods including DSC melting point, crystallinity, GCMS and TGA: crystallinity test results deviate significantly from theoretical values; TGA weight loss analysis is easily affected by rubber adhering to cords; DSC melting point analysis is relatively fast (≈30 minutes) but requires complete sample stripping from tire rubber, posing processing challenges; GCMS structural analysis takes 50 minutes, is unaffected by surface rubber, and requires no sample processing. Thus, GCMS is determined as the laboratory method for identifying nylon 6 and nylon 66.