We develop a low frequency fiber Fabry-Perot[F-P]seismometer based on transfer function analysis.The seismometer structure and demodulation system accuracy are limitations of low frequency seismic monitoring.The transfer function of the F-P seismometer is analyzed,and the mass displacement spectrum[MDS]is introduced.MDS provides guidance for mechanical structure design and optical interferometer analysis to achieve low noise.The F-P seismometer prototype is built.The experiment shows that the prototype has an average noise of 6.74 ng/√Hz below 50 Hz,and its noise is less than that of the global new high noise model within 0.16-50 Hz,whose potential is considerable.