|This paper proposes a new type of active seismometer measuring vibration possessing long period and wide dynamic range. In order to lower the natural frequency and expand the detectable amplitude, the sensor with the low natural frequency is realized by using feedback control. Moreover, to compensate phase-delay, third order phase-lag compensator is added to shape measured output. It has been demonstrated that the detectable frequency range of the sensor is extended from 0.1[㎐] to 10[㎐], while the dynamic range of that is expanded up to 57[㏈], namely vibrations that possess 700times larger amplitude than the maximum stroke of the sensor. New sensor body is produced and tested.