An all-optical quartz-enhanced photoacoustic spectroscopy (QEPAS) system for the highly sensitive detection of acetylene trace gas was proposed. An erbium-doped fiber amplifier (EDFA), a right-angle prism and a fiber Fabry-Perot interferometer (FPI) for out-of-plane one-way vibration detection were employed to improve the detection sensitivity. A self-stabilization technology was used to further improve the stability of the system. The vibration of commercial quartz tuning forks was simulated by the finite element analysis. Parameters such as laser modulation coefficient, structural size of the acoustic microresonator and output power of laser were optimized. A C2H2 minimum detectable limit (MDL) of 2.9 ppb was achieved, with a corresponding normalized noise equivalent absorption coefficient of 2.4×10-9 cm-1·W·Hz-1/2. The 2f signal amplitude shows a good correlation with the C2H2 concentration, with a linear correlation coefficient of 0.999. Finally, a 1-hour continuous experiment verified that the self-stabilization technology can effectively improve the stability of the system.