A compact double-gas sensing system was constructed for the simultaneous sensitive detection of CH₄ and CO_2,which combines quartz-enhanced photoacoustic spectroscopy (QEPAS) and frequency division multiplexing technique. Two continuous wave distributed feedback (DFB) diode lasers operating at central wavelengths of 1654 nm and 2004 nm were employed as the light sources. The photoacoustic signals were first excited by simultaneously injecting sinusoidal modulation currents with independent frequencies near the resonant frequency of the quartz tuning fork into the lasers, and were then demodulated to obtain the corresponding second harmonic components of CH₄ and CO_2,and finally the simultaneous detection of CH₄ and CO₂ was realized. The experimental results showed that there was no disturbance between the photoacoustic signals of these two gases. The relationships of CH₄ and CO₂ concentrations with their corresponding second harmonic signals were calibrated, and a good linear response result was obtained, in which the linear correlation coefficients were all larger than 0.994. The long time measurement of CH₄ with volume fraction of 500×10^-6 and CO₂ with volume fraction of 2000×10^-6 was conducted and the system performance was further evaluated through the Allan deviation analysis. The results indicated that the minimum detection limits of CH₄ and CO₂ for the system were obtained as 0.58×10^-6 and 1.32 ×10^-6, corresponding to the normalized noise equivalent absorption coefficients of 7.2×10^-9 cm^-1·W·Hz^1/2 and 9×10^-9 cm^-1·W·Hz^1/2, respectively.