System identification for cylindrical oil dampers is carried out based on a series of dynamic experimental tests and theoretical approach for the analysis of the experimental data. Experimental tests are conducted using a specific hydraulic actuator in the wide frequency range from 10 Hz to 90 Hz. From this study, it is confirmed that control force of the damper is composed of inertia, damping and restoring components. In general, both restoring and damping components are significant and comparable. However, the portion of the inertia components becomes more significant than to be negligible in the high frequency range.