Abstract: The mechanism of sensitization and spectral response of dyes were investigated by photoconductivity method using AgBr crystal as a model of AgBr emulsion. AgBr crystal with good transparency was prepared by the "crucible-step-down" method. The processes of chemical treatment and the polish of the crystal piece were studied. Results of photoconductivity measurements of AgBr crystal adsorbing dyes used in practice was consistent with the spectral response of photographic emulsion. Moreover it was found that 5, 5’, 6, 6’-tetrachloro-l, 1’, 3, 3’-tetraethylbenzimidazolocarbocyanine apparently differs from other dyes. The results of photoconductivity of AgBr having adsorbed combined dyes with different electric charges showed that the position and height of photocurrent peak in the photoconductivity diagram changed markedly due to the order of adsorption of dyes on AgBr surface, which would be significant for the preparation of photographic emulsion.