Quartz-enhanced photoacoustic spectroscopy technology has the characteristics of zero-background, excitation wavelength independence, compact structure and cost-effectiveness. Compared with conventional photoacoustic spectroscopy, the innovation of the quartz-enhanced photoacoustic spectroscopy is that a quartz tuning fork is employed as an acoustic transducer instead of the wideband microphone. However, the narrow gap size and the high resonant frequency of the commercially available quartz tuning fork prongs limit the abroad application of quartz-enhanced photoacoustic spectroscopy in many fields. To overcome the disadvantage mentioned above, a custom quartz tuning fork which can reduce the resonance frequency while keeping high quality factor was designed. The finite element software COMSOL Multiphysics was used to estimate the stress field distribution along the quartz tuning fork prongs when the quartz tuning fork was designed. The calculation method of resonant frequency is analyzed by combining thr Euler-Bernoulli equation. For a traditional tuning fork quartz, to reduce the resonant frequency of the tuning fork, the length of the prongs should be increased while the width of the prongs should be reduced. At the same time, to obtain a higher quality factor, the width of the prongs must be increased, which results a higher resonant frequency of a tuning fork. Hence, the high quality factor and the low resonance frequency cannot be taken into account at the same time for the traditional shape of tuning fork quartz. From the results of theoretical analysis, the hammer-shaped prongs can optimize the strain field between the prongs and their support effectively. Hence, a quartz tuning fork with hammer-shaped prongs was designed. The homemade quartz tuning fork has the larger gap size ~800 μm between two prongs, which is nearly three times larger than the prongs' gap size of the standard quartz tuning fork. In the meantime, the quality factor and the resonant frequency of the homemade quartz tuning fork were optimized by 14% and 62% respectively, and the compact quartz-enhanced photoacoustic spectroscopy sensor for C₂H₂ detection was demonstrated by using hammer-shaped quartz tuning fork to verify the performance characteristics of the novel custom quartz tuning fork. A near-infrared distributed feedback diode laser with a center wavelength of 6 523.88 cm^-1 and an output power of ～12 mW was served as the C₂H₂ quartz-enhanced photoacoustic spectroscopy sensor excitation source. A so-called acoustic micro-resonator was employed in addition to the hammer-shaped quartz tuning fork for increasing the C₂H₂ quartz-enhanced photoacoustic spectroscopy signal amplitude via the acoustic resonance effect. The acoustic micro-resonator was assembled in an “on-beam” quartz-enhanced photoacoustic spectroscopy configuration, in which the acoustic micro-resonator was formed by two metallic thin tubes and was coupled to the homemade quartz tuning fork via the excited sound wave in gas contained inside the acoustic micro-resonator tubes. Both the length and assembly position of the acoustic micro-resonator were optimized in terms of signal amplitude and signal-to-noise ratio. And the two parameters mentioned above were selected to be 9 mm and 1.5 mm by experiment respectively. The second-harmonic detection technique was employed to reduce the sensor background noise and simplify the data process. The wavelength modulation depth was optimized at room temperature and atmospheric pressure. The hammer-shaped quartz tuning fork based C₂H₂ sensor achieved a minimum detection limit of 282×10^-9 for a 300 ms averaging time and 12 dB/oct filter slope, which corresponds to a normalized noise equivalent absorption coefficient of 3.84×10^-9$\mathrm{c}{\mathrm{m}}^{-\mathrm{1}}\mathrm{W}/\sqrt[]{\mathrm{H}\mathrm{z}}$. The results mean that the detection sensitivity was improved by a factor of about one order of magnitude, compared to the case of a sensor using a commercially available quartz tuning fork.