A method for detecting or comparing mechanical strength of macro-molecular polymer materials. The detecting method has the steps of measuring the mechanical strength and the maximum value of the fluorescence absorption spectrum of each of the plurality of samples to form a curve relationship or function relationship between the maximum value of the fluorescence absorption spectrum and the mechanical strength; measuring the maximum value of the fluorescence absorption spectrum of the target material, and using the curve relationship or the function relationship to obtain the mechanical strength of the target material. The plurality of samples and the target material are both prepared from a macro-molecular polymer, and the macro-molecular polymer may be composed of disulfonate-difluorobenzophenone, hydroxyindole and difluorobenzophenone as monomers, and the sulfonate groups of the disulfonate-difluorobenzophenone have metal cations. An object of the method is to identify mechanical properties of polymer materials by fluorescence nondestructive detection.