A new electromagnetic active vibration absorber was desiggned by using an electromagnet as the actua- tor，and its force characteristics was studied． Firstly，the mathematical model for electromagnetic force of actuator was built． Secondly，the kinematical equation of the active vibration absorber was deduced based on the mathe- matical model，and the characteristics of electromagnetic force and driving force was analyzed． Finally，conside- ring the inevitable variance between the practical driving force and the ideal driving force of active vibration absor- ber，the influence of the variance in amplitude，phase and frequency on the performance of the active vibration ab- sorber was analyzed analytically． Experiment bench for a plate was set up，and the theoretical analysis has been verified by experiments． The results show that the greater the amplitude and phase variance between the practical driving force and the ideal driving force is，the poorer the damping effect is; when there is frequency variance，ac- tive vibration absorber has no damping effect．