Methods for determining the sensitivity of fluorescent probes and their classification with respect to sensitivity and specificity using human serum albumin as a reference protein and 8-anili-nonaphthalenesulfonate, K35 and pyron red as probes are proposed. The indicators of sensitivity and specificity of fluorescent probes as markers of the structural state of proteins are the activation of the probe fluorescence in excess of protein and the constant of its binding to the strong highly affine center of protein sorption. Fluorescent probes as markers of the binding ability are assessed by a protein-dependent increase in fluorescence under the conditions of excess probe and from the constant of its binding to weak secondary binding sites of the protein.