After friction sensitivity test of TATB pellet, the working surface of the steel pillar wouled be coloured in some extent. In order to verify if it was resulted from the explosive ignition, the TATB pellets were compressed in situ on the friction device with the test tools under different conditions and then check the pillar surfaces and TATB examples compressed. Even though the pillars were coloured after compressing TATB pellets in some cases,the IR spectrum analysis indicated,there were not any chemical reaction occured,The different colours were the result of light interference from the TATB film formed on the surface during the pellet compression.The desensitization effect of TATB is discussed herein.