The present invention discloses a catalyst system used for acetic acid and acetic anhydride synthesis and the application. Halide of rhodium is used for active specie of a catalyst and alkyl halide, alkali metal iodine and organic solvent are used as the catalyst. Caffeine is used as a ligand. The mass proportion of the caffeine and the halide of the rhodium is one till thirty to one. The catalyst system provided by the present invention has the advantage of good compatibility. The hard removing problems of the wall attachment, the falling to the bottom and the coking of the catalyst are not easy to happen in carbonylation reaction equipment. And the present invention has the advantages of high catalytic activity, high selectivity, high thermal stability and strong anti-coking performance. Any complex pretreatment before the catalysis is not needed. The formation of the catalyst system is simple and rapid. The catalyst process is simple and easy to be implemented. And the present invention also has the advantages of high catalytic activity, high stability, good compatibility, low cost, etc.