In the time-division multiplexing fiber-optic hydrophone system, it is desired to design the signal detection circuit with large gain and bandwidth. In order to reduce the system noise while suppressing crosstalk between channels, you must select the appropriate circuit bandwidth. This paper analyzes the relationship between the bandwidth and the pulse shape of the signal to be detected and the relationship among circuit bandwidth, pulse width, channel interval, and circuit crosstalk ratio, and gives the analytical expression of the crosstalk ratio. Formulae of demodulated signal error caused by circuit crosstalk are derived, and the result is that the amplitude of the demodulated signal error is proportional to the circuit crosstalk ratio and the Bessel function of the amplitude of the acoustic signal added to the previous channel. The experimental results are consistent with the theoretical analysis.