An acoustic sensitization method based on a fiber-wrapped thin-walled cylinder is studied. The sound pressure sensitivity calibration experiment system is established based on a 3×3 coupler. The directional characteristics of a thin-walled cylinder are experimentally investigated. The influence of the cylinder radius and wall thickness on the acoustic sensitization of fiber is studied experimentally, and the sound pressure sensitivity reaches 1.338 rad/Pa (-117.47 dB re rad/Pa). Then, the fiber-wrapped thin-walled cylinder is applied to a quasi-distributed acoustic sensing system for testing. For a 20.06-km sensing distance, the error between the 1-kHz sinusoidal applied waveform and experimental recovered waveform is below 4.1%. The signal-to-noise ratio (SNR) is 21.03 dB higher than that of unsensitized fiber coil sensing, showing the effect of the acoustic sensitization sensing of the thin-walled cylinder. The results provide an experimental basis for further developing high-sensitivity quasi-distributed acoustic sensing.