A method for analyzing a gas, in order to estimate an amount ( c k) of a plurality of different gaseous species ( G k), called the candidate gaseous species, potentially present in the gas, each candidate gaseous species being able to absorb light radiation in an absorption spectral band (Δ x), the method comprising the following steps: a) placing the gas between a light source and a light sensor, the light source being able to emit illuminating radiation that propagates through the gas, the light sensor being able to detect radiation transmitted by the gas and to deliver a detection signal representative of an intensity ( I j) of the detected radiation; b) illuminating the gas using the light source, the radiation illuminating the gas having an illumination spectrum ( S j), the illumination spectrum extending continuously in a spectral band, called the illumination spectral band (Δ 12), covering the absorption spectral band (Δ x) of a plurality of candidate gaseous species; c) during the illuminating step, detecting, with the light sensor, a radiation transmitted by said gas; d) reiterating steps b) and c), while adjusting the light source such that, in each step b), the illumination spectrum ( S j) is modified; e) estimating an amount ( c k) of each of the candidate gaseous species depending on the intensities ( I j) of the radiation detected in each step c), respectively, each intensity ( I j) being associated with one illumination spectrum ( S j); wherein: in each step c), the radiation transmitted by the gas is detected in at least a same detection spectral band (Δ 20), extending continuously between a minimum wavelength ( λ 20-min) and a maximum wavelength ( λ 20 -max), with a spectral width of at least 1 μm, and covering absorption spectral bands (Δ x) of a plurality of candidate gaseous species; and in each iteration of steps b) and c), the illumination spectrum ( S j), extending continuously in the illumination spectral band, is modified within the same illumination spectral band (Δ 12). a) placing the gas between a light source and a light sensor, the light source being able to emit illuminating radiation that propagates through the gas, the light sensor being able to detect radiation transmitted by the gas and to deliver a detection signal representative of an intensity ( I j) of the detected radiation; b) illuminating the gas using the light source, the radiation illuminating the gas having an illumination spectrum ( S j), the illumination spectrum extending continuously in a spectral band, called the illumination spectral band (Δ 12), covering the absorption spectral band (Δ x) of a plurality of candidate gaseous species; c) during the illuminating step, detecting, with the light sensor, a radiation transmitted by said gas; d) reiterating steps b) and c), while adjusting the light source such that, in each step b), the illumination spectrum ( S j) is modified; e) estimating an amount ( c k) of each of the candidate gaseous species depending on the intensities ( I j) of the radiation detected in each step c), respectively, each intensity ( I j) being associated with one illumination spectrum ( S j); in each step c), the radiation transmitted by the gas is detected in at least a same detection spectral band (Δ 20), extending continuously between a minimum wavelength ( λ 20-min) and a maximum wavelength ( λ 20 -max), with a spectral width of at least 1 μm, and covering absorption spectral bands (Δ x) of a plurality of candidate gaseous species; and in each iteration of steps b) and c), the illumination spectrum ( S j), extending continuously in the illumination spectral band, is modified within the same illumination spectral band (Δ 12).