Abstract: A new method of catalytic kinetic fluorometry has been established for the determination of trace amounts of cadmium. It is based on the catalysis of both Cd(Ⅱ) and imidazolc on the reaction of complex formation between Co(Ⅲ) and α,β,γ,δ-tetrakis(4-sulphophcnyl) porphine [T(4-SP)P] in H₃BO₃-Na₂B₄O₇buffer solution with pH8.5. Fixed time method is used in measuring the reaction rate. The concentration of the product, Co(Ⅲ)-T(4-SP)Pcomplex, is monitored by measuring the flourescence intensity of T(4-SP)Pwhich is decreased as the concentration of the product increases. The calibration graph is rectilinear over the concentration range of 0-16 ng Cd(Ⅱ)/ml. The limit of detection is 0.5 ng Cd(Ⅱ)/ml, the accuracy of determination,±6%. Eight replicate determinations of solutions containing 0.2μg Cd(Ⅱ) show a relative standard deviation of 4.3%.