Extrinsic fiber Fabry-Perot acoustic sensors consisted of quartz diaphragm and end of pigtail were performed on acoustic measurement under water. The characteristic of amplitude-frequency and sensitivity of the sensors were argued in the paper. Because quadrature-point of the Fabry-Perot sensors affected the system output

the characteristics of output signals were analyzed in different conditions. The Fabry-Perot sensors were subjected hardly to fluctuation of source power and their resonant frequency were higher than other sensors. So this kind of sensors was one of choices on acoustic measurement under water well.