This work demonstrated quantitatively that DSA (dansylamide) and apo CA (dezincified carbon anhydrase) interacted with each other in the presence of Zn2+ (zinc ion). Thefl uorescence emission of DSA in the presence of Zn2+ and the intensity offl uorescence, which was proportional to the concentration of Zn2+, could be used in the measurement of Zn2+ concentration. Considering that Zn2+ was the active center of enzymes like CA (carbon anhydrase), two dezincifi cation reagents were compared to ensure the validity of our method. A certain range concentration of Zn2+ could be measured by the reaction product of apo CA, DSA and Zn2+, where the measurement limitation was about 60 nmol/L. Interaction of CA with DSA was also studied with infrared spectrometry.