The research was made on ultra-deep removal of thiophene compounds in diesel oil over catalyst assisted by ultraviolet irradiating (URTCU). The model compounds were thiophene, benzothiophene, dibenzothiophene and 4,6-dimethyl-dibenzothiophene. ZSM-5 zeolite was modified by Ti and Ni. X-ray diffraction (XRD) showed the ZSM-5 remained intact after modification. The effect on the desulfurization rate was studied of catalyst/oil ratio, reaction temperature, the space velocity, reaction pressure and the oxidant amount. Under the optimized conditions, the removal rate of the sulfur model compounds approached to 100%. Meanwhile, the desulfurization mechanism of URTCU was explored. (C) 2012 Elsevier Ltd. All rights reserved.