Abstract: Surface(Enhanced Raman Spectra (SERS) of free(base tetraphenylporphyrin (H2TPP) and its Ag(, Mg(chelates (AgTPP and MgTPP) adsorbed on AgBr colloid were studied by 632.8 and 488.0nm excitation. The SERS results show that the adsorbed MgTPP (or H2TPP) molecules undergo silver(exchange (or silver(incorporation) reaction to form AgTPP. The chavge transfer mechanism is believed to be the major origin of Raman enhancement for both 632.8 and 488.0nm excitation lines. For 488.0nm excitation, additional mechanism of electronic pre(resonance effect also contributes to the Raman enhancement, resulting in a slightly different SERS spectra compared with 632.8nm excitation.