A cantilever-enhanced photoacoustic signal detection method based on fiber-optic Fabry-Perot interferometric sensors is proposed, which combines the technologies of fiber-optic sensing, longitudinal resonant photoacoustic spectroscopy, wavelength modulation and second-harmonic detection. According to the characteristics of fiber coupling near-infrared exciting light, the resonant photoacoustic cell is optimally designed. A high-sensitivity laser photoacoustic spectrometer for trace acetylene gas detection is developed. Experimental results show that the detection limit of acetylene reaches 8×10-10 with the measurement time of 60 s.