The multi-spectral imaging system for real-time measurement of combustion efficiency of an industrial flare is provided. The system includes four spectral bands, one for a hydrocarbon group (fuel), one for carbon dioxide (CO2), product of complete combustion), one for carbon monoxide (CO, product of partially completed combustion), and one for background reference. More spectral bands can be added to measure combustion efficiency of specific compounds or enhance the background reference adjustment. The analysis apparatus includes a machine readable storage medium, which provides instructions that cause the analysis apparatus to perform operations to obtain the combustion efficiency of the flare. The operations includes acquiring at least three spatially and temporally synchronized intensities from an imaging unit capturing images of the flare, and producing the combustion efficiency of the flare from said at least three intensities, and absorption coefficients of materials contained in the flare.