A computational model for a high speed vehicle with early defects in axle box roller bearings was established using the dynamic package SIMPACK. It was assumed that there only existed interactions between the outer ring and inner ring for the bearing, so that the bearing rollers were directly equivalent as several force elements. Then，the early defects located on the inner and outer rings and roller surfaces were considered and their influences on the vertical vibrations of the vehicle system were analyzed. The simulation results show that the axle box bearing defects increase the axle box acceleration significantly, but has little effect on the bogie frame acceleration. when the defect size produced by the three kinds of defects are equal, the defect located on the outer ring surface has the greatest influence on the amplitude of the axle box acceleration, but the defect on roller surface has the least effect. With the increasement of defect width, the amplitude of axle box acceleration under three kinds of bearing surface defects both increases gradually. The bearing early defects can cause high-frequency vibrations of the axle box，but almost has no effect on the vehicle ride comfort.