The correlation spectroscopy principle and the methane detection system ba sed on cheap infrared(IR) broadband light source are introduced in this paper,and methane spectral absorption simu lations for different concentrations are carried on by using HITRAN database.Combined with the parameters of a gas chambe r with a photodetector,the relationship between the system detection limit and light intensity is obtained.The system noise is processed by FFT coupled with Savitzky-Golay filtering algorithm during the actual measurement f or different methane concentration gradients,and the noise caused by external factors is reduced by one order of ma gnitude.The relationship between methane concentration and intensity modulation index is obtained by linear fitting,and the system can achieve precise results in methane detection.The measurement errors ranged from 1.5% to 7%,and accurate det ection to the methane concentration was achieved.