A photoacoustic spectroscopy multi-gas detection system based on infrared heat radiation light source was developed. The broadband mid-infrared thermals radiation source and band-pass filter were used to generate the photoacoustic excitation light. Combined with a small-volume non-resonant photoacoustic cell， the time-sharing measurement of multi-component gas concentration was realized. The parameters of the mid-infrared bandpass filter were determined by analyzing the main factors of cross-interference among multi-component gases and the infrared absorption spectrum of target gases. To determine the quantitative relationship of cross interference among the gases to be measured， the photoacoustic spectrometer system was calibrated by using the standard gas， and a humidifier was used to analyze the interference from water vapor. The experimental results showed that the interference levels of C₂H₂ to CH₄ and CH₄ to C₂H₆ reached 10.49 μV/（μL/L） and 18.66 μV/（μL/L） respectively， and the interference between other hydrocarbon gases can be ignored. The responsiveness of CO₂ to CO， CH₄， C₂H₂ and C₂H₄ interference was 1.615 μV/（μL/L）， 0.055 μV/（μL/L）， 0.130 μV/（μL/L） and 0.016 μV/（μL/L）， respectively. In addition， water vapor will cause certain interference to C₂H₂， CH4， C₂H₆， C₂H₄， CO and CO₂， and the responsiveness of the interference was 0.591 μV/（μL/L）， 0.421 μV/（μL/L）， 0.071 μV/（ μL/L）， 0.007 μV/（μL/L）， 0.051 μV/（μL/L） and 0.055 μV/（μL/L）. The experimental results indicated that there was a high level of interference when detecting CH₄ in C₂H₂ background， C₂H₆ in CH₄ background， CO in CO₂ background， and other target gases in high concentration water vapor background， which should be considered in the measurement process.