Platinum group metal dichalcogenides (PtTe2) with controllable thickness have been synthesized and confirmed to be promising electric and spintronic materials. Here, using the first-principles calculations, we demonstrate the potential application of PtTe2 as catalyst substrate. Taking CO oxidation as model reaction, the importance of surface vacancy is clarified. It is found that surface vacancy on PtTe2 could improve the stability and catalytic activity of the supported Pt atom. The details of CO oxidation processes indicate that surface vacancy could weaken the adsorption of reactants and speed up the formation and decomposition of OOCO intermediate on Pt catalysts. The underlying mechanisms for the improved activity are unveiled through comprehensively analyzing the charge transfer, density of states, and charge density difference. We hope that the current findings were beneficial for the research and development of efficient catalysts by collocating various single atom/cluster catalysts with different platinum group metal dichalcogenides.