It is suggested to use cholesteric-nematic mixture as a sensitive medium of optic sensor for amino acids. After addition of amino acids or their aqueous solutions, the mixture changes its spectral properties, which is the basis for creation of sensitive medium of optic sensor for amino acids. Linear range of the change of wavelength of minimum transmission of elaborated cholesteric-nematic mixtures due to the concentration of powder-like proline, histidine and arginine has been established; specificity of their interconnection has been analyzed.