The present invention relates to a vanadium-based catalyst system for olefin polymerization, wherein the vanadium-based catalyst system comprises a vanadium compound main catalyst, an organoaluminum compound auxiliary catalyst and a compound regulator containing a carbon-halogen chemical bond. According to the present invention, the vanadium-based catalyst system for olefin homopolymerization and copolymerization of ethylene with other olefins or diolefins has high catalytic activity so as to reduce the catalyst consumption; and the random sequence distribution content in the prepared copolymer is increased, and the comonomer insertion rate is significantly improved.