The work aims to study the change of square resistance of conductive pattern after near infrared sintering under different conditions. Firstly, screen printing was used to print patterns on PET substrates, paper substrates and cotton substrates; Secondly, the near infrared sintering test was carried out by increasing the sintering time and whether to add reflector or not; Finally, the square resistance of the sintered conductive pattern was measured with four-point probes, and then the test data were analyzed. It turned out when the sintering time increased to 13 seconds without reflector, the square resistance of the conductive pattern on the PET substrate remarkably decreased from 381 mΩ/□ to 89.25 mΩ/□, and the square resistance of the conductive pattern on the paper substrate markedly decreased from 290.3 mΩ/□ to 132.5 mΩ/□. After 10 seconds of sintering, the square resistance of the conductive pattern on the cotton substrate reduced from 357 mΩ/□ to 111 mΩ/□. When adding the reflector, the square resistance of the conductive pattern on PET substrate reduced from 381 mΩ/□ to 72.7 mΩ/□ within 5 seconds and the square resistance of the conductive pattern on paper substrate decreased from 290.3 mΩ/□ to 62.5 mΩ/□. In conclusion, the near infrared sintering is suitable for the three flexible substrates mentioned above, and the addition of reflector can significantly enhance the infrared thermal effect and rapidly reduce the value of square resistance.