This article presents a novel cavity-enhanced photoacoustic dual-comb spectroscopy (DCS) method for ultrasensitive, broadband, and high-resolution molecular spectroscopy and trace gas detection. The technique combines a high-finesse optical cavity for power amplification of dual-frequency combs and a broadband acoustic resonator with a flat-top frequency response. The method enables high-resolution spectroscopic measurements of trace amounts of C₂H₂, NH₃, and CO in the entire telecommunications C-band. The minimum detection limit for C₂H₂ is 0.6 ppb, corresponding to a noise equivalent absorption coefficient of 7×10⁻¹⁰ cm⁻¹. The proposed method overcomes the limitations of conventional DCS by enhancing the power of dual-comb light and using a broadband acoustic resonator for effective amplification of acoustic waves. The system demonstrates a 3-dB bandwidth of over 5 kHz in the audio frequency range of 2.7–8.0 kHz. The broadband acoustic resonator is designed to amplify many acoustic waves with distinct frequencies. The method also shows a significant improvement in detection sensitivity, achieving sub-ppb levels for C₂H₂ and NH₃. The system's high-finesse cavity enhances the optical power of hundreds of comb pairs by nearly three orders of magnitude. The method enables comb-line-resolved DCS measurements of trace amounts of C₂H₂, NH₃, and CO in the entire telecommunications C-band. The results demonstrate the feasibility of significantly enhancing the comb power by coupling both frequency combs into a high-finesse optical cavity. The system also shows a good linear response with an R² value of 0.9976. The method has potential applications in broadband, high-precision, and high-sensitivity spectroscopic measurements and gas sensing.This article presents a novel cavity-enhanced photoacoustic dual-comb spectroscopy (DCS) method for ultrasensitive, broadband, and high-resolution molecular spectroscopy and trace gas detection. The technique combines a high-finesse optical cavity for power amplification of dual-frequency combs and a broadband acoustic resonator with a flat-top frequency response. The method enables high-resolution spectroscopic measurements of trace amounts of C₂H₂, NH₃, and CO in the entire telecommunications C-band. The minimum detection limit for C₂H₂ is 0.6 ppb, corresponding to a noise equivalent absorption coefficient of 7×10⁻¹⁰ cm⁻¹. The proposed method overcomes the limitations of conventional DCS by enhancing the power of dual-comb light and using a broadband acoustic resonator for effective amplification of acoustic waves. The system demonstrates a 3-dB bandwidth of over 5 kHz in the audio frequency range of 2.7–8.0 kHz. The broadband acoustic resonator is designed to amplify many acoustic waves with distinct frequencies. The method also shows a significant improvement in detection sensitivity, achieving sub-ppb levels for C₂H₂ and NH₃. The system's high-finesse cavity enhances the optical power of hundreds of comb pairs by nearly three orders of magnitude. The method enables comb-line-resolved DCS measurements of trace amounts of C₂H₂, NH₃, and CO in the entire telecommunications C-band. The results demonstrate the feasibility of significantly enhancing the comb power by coupling both frequency combs into a high-finesse optical cavity. The system also shows a good linear response with an R² value of 0.9976. The method has potential applications in broadband, high-precision, and high-sensitivity spectroscopic measurements and gas sensing.