To solve the problem that single eccentric vibrator causes horizontal direction force，a double eccentric vibrator is proposed and differential equations of the 4 DOF vibration system of the compacting mechanism are established to analyze the system’s natural frequencies. The state space model of compacting mechanism is constructed and the parameter variety’s influence of tamper，vibrator and compacting beam on the dynamic characteristics is analyzed by MatLab/Simulink. The results indicate that double eccentric vibrator provides double pressure，and the system’s natural frequency reduces while the quality of screed increases. Besides，the parameters of compacting beams and tamper have more influence on the dynamic characteristics of compacting mechanism than that of vibrator. Therefore，the parameter adjustment of tamper and compacting beam should be paid more attention to obtain optimal effect.