Abstract: The relationship between riding comfort and pavement roughness were studied from the view point of the road users in this research.RMSSD was selected to study passengers' riding comfort as a main evaluation index.In this study,12 pavement sections with roughness changing from 1.06 to 5.53 m/km were selected to conduct on driving test in field.Test results show that,under different driving speed RMSSD changes obviously when the pavement roughness changes.In combination with the subjective scoring method and acceleration evaluation method,the critical value of roughness based on comfort considerations is proposed at different speeds.