A new catalyst system V-Cs-Cu-T1/TiO2 . SiC for vapor-phase selective oxidation reaction of p-tert-butyltoluene to p-tert-butylbenzaldehyde were studied. It was found that the addition of thallium promoted the reaction. After 365 hours stability test, the V-Cs-Cu-T1/TiO2.SiC catalyst still kept excellent result that conversion of p-tert-butyltoluene and the selectivity of p-tert-butylbenzaldehyde reach 10 mol% and 80 mol%. The catalyst was characterized by XRD, TEM, FT-IR and ICP measurements.