The invention mainly belongs to the technical field of higher organism genome editing, and particularly relates to an establishment method of a T7-RNA-polymerase-mediated CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 gene editing system. The method is based on the highly specific recognition principle for the T7 RNA polymerase and T7 promoter, and comprises the following steps: establishing T7 promoter-sgRNA, transforming the T7 promoter-sgRNA, a Cas9 expression plasmid and a T7 RNA polymerase expression plasmid into cells, and catalyzing the T7 promoter to promote the transcription of sgRNA by using the T7 RNA polymerase so as to guide the Cas9 to perform cutting at the target, thereby completing the gene editing process. By using the T7 promoter to express the sgRNA, the method simplifies the design steps of the CRISPR/Cas9 system, so that more people can quickly and easily research the interested gene locus by using the CRISPR/Cas9 gene editing tool.