Phase-sensitive detection circuit tests signals according to the correlation of the reference signal and the input signal. The noise is eliminated by the independence between the reference signal and the noise signal. The sensitivity of the detector is improved significantly by the suppression of the noise. In this work, a phase-sensitive detection circuit is designed for seismometer, which possesses the characteristics of low-input noise, variable-output gain and high sensitivity. The feasibility of this phase-sensitive detection circuit is verified by the Multisim and the signal-to-noise ratio is satisfactory.