Fresnel lens can realize both focus and dispersion of light and it also has the virtues including small volume, light weight and reproducibility, which makes it be widely used in spectral inspection. Typical spectral imaging instrument with Fresnel lens obtains continuous spectral lines by moving Fresnel lens along optical axis and therefore it will greatly decrease the stability of the whole instrument. Considering the requirement of gas detection, multi-channel mode was adopted to obtain multi-spectral and a novel infrared gas sensor based on a Fresnel lens array was presented. The gas sensor can real-time check and inspect of CO2, CO, CH4 and SO2 gases, whose adsorption wavelengths are all within from 3 μm to 5 μm infrared waveband. The relationship of spectrum resolution of Fresnel lens with structure parameters of lens was deduced by use of transmission theory of spherical wave and Rayleigh criterion. Moreover, structure parameters and their fabrication errors for 1 μm fabricated and eight phased Fresnel lens array were calculated when spectral resolution is required to be less than 50 nm. The calculated results show that the focal length of lens array is required to be 47.84 mm and the average numerical aperture can be more than 0.4.