Based on field tests of high-speed coaches X and Y, the characteristics and mechanisms of the abnormal interior noise and vibration occurred in the type X coach are investigated. In the field tests, the test coaches are running at the same operation speed and similar exterior air turbulence and track excitation. The two types of coaches are contiguously marshaled in the adjacent positions of a same train, both of which are motors. A long-term monitoring and analysis of the wheel wear status and the interior vibration-noise of coaches X and Y marshaled in trains are conducted focusing on the relationship between the interior abnormal noise and the non-circular wear of wheels. The test results shows that the type X coach generates higher abnormal vibration and noise than type Y coach. The abnormal vibration and noise are sensitive to the high-order polygonal wear of the coach wheels. It is also found that the higher vibration and noise on type X coach is related to its special interior structural.