Methane (CH₄) is the main component of mine gas and one of greenhouse gases, and the measurement of CH₄ concentration is of great significance for industrial production safety and human health security. In this paper, an on-beam quartz tuning fork enhanced photoacoustic spectroscopic system for CH₄ detection was proposed, and a quartz tuning fork with a high quality factor was used to overcome the shortcomings of the traditional photoacoustic spectroscopy where microphones were susceptible to environmental noise. Furthermore, a miniaturized gas chamber with a volume of only 3 cm×2 cm×1 cm was developed, which simplified the structure of the detection system. Combining the wavelength modulation technology, we analyzed the relationship between the amplitude of second harmonic (2f) signal and the modulation depth. The experimental results demonstrate that the amplitude of optimal modulation signal was 0.175 V and the corresponding modulation depth was 0.169 cm ^-1. In addition, the CH₄ volume fraction in the range of 5×10 ^-4-5×10 ^-3 and the 2f signal amplitude were fitted and their linearity was found to be 0.99791. Besides, the stability of the system was analyzed based on Allan variance. When the average time was 5 s, the 1σ lower detection limit of the system was 4.337×10 ^-5. In summary, the photoacoustic spectroscopic gas sensor based on a small-volume photoacoustic gas cell has the advantages of small size, light weight and low cost, which is more suitable for portable sensing applications.