Optical interference signal is relatively weak which is produced by the fiber bragg grating strain, Demodulating optical signal that cannot be directly applied to the corresponding signal, The amplifier circuit of low noise, high gain and high frequency is designed to process the weak light. To verify the circuit parameters are determined by simulation, after the design and related debugging of the circuit, photoelectric conversion completed preamplifier and subsequent amplification circuit which can better realizes the photoelectric conversion and amplification. The dynamic stain signal is demodulated, The voltage data with strain signal acquisition and processing, the design of the weak light signal detection system is proved that has the practical value.