A broadband gas sensing technology is reported. The measurement principle relies on Fourier transform photoacoustic spectroscopy (FT-PAS) using a differential photoacoustic cell, in which both phase modulation and amplitude modulation are simultaneously applied to the broadband light sources. The thermal light source and supercontinuum source are employed sequentially. The performance of the FT-PAS is demonstrated by measuring the spectra of methane in the 2–10 µm range and acetylene in the 1–2 µm range. By leveraging the wavelength-independent nature of the photoacoustic effect, this system holds promise for comprehensive full-spectrum spectral detection.