A single moving mass-spring-damper model is adopted to simulate the vehicle model. The equation of vehicle-bridge coupling vibration is derived, using D'Alembert principle and the conditions of displacement compatibility. The dynamic responses of a double cable suspension bridge to the vehicle moving at different speeds are analyzed, considering the geometric nonlinearity and the bridge carriageway irregularity factor, under two types of vehicle loading conditions, namely moving along the center and the eccentric longitudinal axis. Then the influence of vehicle velocity and bridge carriageway irregularity on impact coefficient of double cable suspension bridge is discussed. Single cable suspension bridge can be taken as a special case of double cable suspension bridge, after the main cable shape coefficient is introduced. The dynamic responses of double cable suspension bridge and single cable suspension bridge are compared to reveal the character of vehicle vibration of double cable suspension bridge. The study of the dynamic responses character of double cable suspension bridge has a positive significance on structural form selection of such type bridge during designing, dynamic performance evaluation and vibration control.