In this project,the concentration of caffeine in coffee in water solution is investigated.rnThe molar decadic absorption coefficient in water is determined by preparing severalrnconcentrations and applying least square method. The obtained result is 1098.87rnm2rnmol . The constant that relate the absorbance of caffeine in coffee in water solutionrnto the extracted caffeine is developed and its value is ( 2.9 mg−1). Moreover bandrndeconvolution method is developed to remove the interfering matrix elements in thernabsorption spectrum of coffee in water solution. To apply this method the interferingrnband is modelled by a convolution of five gaussian functions. The result obtainedrnusing this technique is consistent with other results with an error of 5−8%. Finally thernconcentration of caffeine in coffee seed is determined by correlating the fluorescencernintensity of the emission spectrum of pure caffeine and coffee powder in water solutionrnby applying quenching fluorescence. After all these methods are applicable in everyrnpart of the country to determine the concentration of caffeine in coffee seed with leastrncost using a universal solvent,water.rnKey words: Caffeine, deconvolution, interfering band, gaussian model, absorbance,rnUV/Vis, and fluorescence