Coumarin derivatives with imino groups were synthesized by using 8-formyl-7-hydroxylcoumarin-3-carboxylic acid ethyl ester and 2-aminophenol as raw materials, then the coumarin- copper ions coordination compounds fluorescent probe was made after the complexation of the derivatives and copper ions. In 50% ethanol aqueous solution, this probe shows a good selectivity to the kind of amino acid with thiols. The measurement mechanism of determination was explored by studied the fluorescence spectrum. During the recognizing of the probe, its fluorescence intensity whose visual colour was changed from green to blue, becomes more and more stronger. Thus, the visual detection was achieved by this method.