The invention discloses a method for constructing an efficient expression vector through combination of a high CG (cholyglycine) fragment and a promoter of a low CG content. According to the method, apromoter which contains an enhancer and has a CG content less than 50% at the upstream of a transcriptional start site is selected as a target promoter, a CMV (cytomegalovirus) promoter in an exogenous gene expression frame on a commercial vector pEGFP-C1 (plasmid enhanced green fluorescent protein-C1) is replaced by the target promoter to construct an intermediate vector, 1-1.5kb of a CG fragment U1 which has a CG content greater than 70% is inserted into an Ase I restriction enzyme cutting site in front of the exogenous gene expression frame of the intermediate vector to construct an expression vector, and verification shows that the expression vector is capable of enabling an EGFP gene in a target promoter expression frame to be continuously, stably and efficient expressed. The methoddisclosed by the invention is applicable to the field of industrial production of antibodies and protein medicines or gene treatment, is capable of improving the production efficiency and reducing theproduction cost, or can be applied to the field after further improvement.