In light of the changeable primary mode interval of ultra-long stay cable vibration, the inertial damper of magnetic particle clutch has greater advantages as a semi-active inertial damper than as a passive inertial damper. Existing research, however, indicates that simply injecting direct current into the magnetic particle clutch's inertial damper would not be sufficient to realize the Constantvalue regulated function of the damper's inertial coefficient. This function will be accomplished in this study by inputting harmonic current.. First, the fundamental operation and mechanical features of the magnetic particle clutch's inertial damper are described. From the relative motion state of the two magnetic particle clutch axes, the mechanical characteristics are evaluated, and the control method for the input current to realize the adjustable function of the inertial coefficient of the damper of the damper is explored. The equivalent inertial coefficient of the damper under steady-state excitation is then expressed, and the mechanical model of the damper is developed based on the damper's fundamental structure. The equivalent inertial coefficient of the damper under input control current and the amplitude of the control current are eventually shown to have a quadratic linear relationship.Lastly, the inertial coefficient of the damper's adjustability was verified experimentally.