Aiming at the phenomenon of abnormal noise about a type of electric locomotive cab, the vibration and noise of related parts were tested. The wheel vibration characteristics, carbody vibration transmission performance, cab structure mode and cavity mode were analyzed, and the possible causes of abnormal noise were obtained, which was pointed out that the low-frequency vibration caused by polygonal misalignment was the main causes for the excessive vibration of cab, the sound and solid coupling vibration between the vibration frequency of the cab panel and cavity mode was the fundamental cause of the abnormal noise of electric locomotive.