Abstract: Pass-by noise is the main form of external noise produced by vehicles during the driving process,and it is also one of the important indicators to judge its ability to run on road or off road. Based on the order analysis technique,this paper tests the pass-by noise of a tractor,analyzes the vibration and noise characteristics of the tractor components with the test result,finds out that the main contribution of tractor pass-by noise is fan noise,gearbox noise or both,and then can effectively reduce the tractor pass-by noise by controlling fan speed and gearbox whistle.