Abstract: In this paper, the abilities of ms-tetra (2-imidazolyl) porphyrin and ms-tetra (4 or 5-imidazolyl) porphyrin to form metal complexes with zinc cation have been compared with that of ms-tetraphenylporphyrin. The catalytic activities of metal complexes of ms-tetraimi-dazolylporphyrins have been investigated in the oxidation of hydroquinone, isopropylmercap-tane and ascorbic acid with molecular oxygen. The net charge distribation and orbital energy of H₂P, H₂TPP, H₂T(5-I)P and their zinc complexes have been calculated with EHMO programe. The data explained the experimental results satisfactorily. The results showed that the complex abilities of the porphyrins and the catalytic activities of their metal complexes increased after the imidazolyl groups were introduced into the porphyrin ring.