The application of fiber Bragg grating(FBG) sensing technology in traffic detection system and the problem of the temperature cross sensitivity in FBG strain sensing were discussed. The structure and principle of the FBG sensor were theoretically analyzed, and the experiment system was constructed through making experiment investigation, the ideal experiment results were ultimately obtained after many tests. Several experiments on different types of vehicles proved that the accuracy rate of the identification system could be arrived at 100%, which is perfectly matched with the principle. This system has the merit of resistance to damp and dust, anti-electromagnetic interference, and it is hopeful for replacing the existent electric products. The system has been widely applied in practical engineering.