The transient photo-sensitive oxidation between 2-methylanthraquinone (MAQ) and aromatic amino acids (namely tryptophan, tyrosine and phenylalanine) in acetonitrile/water (1∶1, V/V) solution was investigated by laser photolysis techniques with the excitation wavelength of 355 nm. The triplet state absorption of 2-methylanthraquinone was attributed to 390, 450 and 590 nm and the anion radical absorption of MAQ was due to 390 and 490 nm identified by the electron transfer reactions from 4-diazabicyclo ［2.2.2］ octane (DABCO) or diphenylamine (DPA) to 3MAQ*. With the decay of 3MAQ*, the MAQ·- at 490 nm appeared, which indicated that the electron transfer reactions between 3MAQ* and amino acids occurred. Moreover, the rate constants were deduced to be 3.0×109, 1.1×109 and1.8×108 L·mol-1·s-1 for TrpH, TyrOH and PHE, respectively. On the other hand, the free energy changes (ΔG) of the reactions showed that the proposed electron transfer steps are thermodynamically feasible.