Under the guidance of the above ideas, in this work, we used the PSA promoter to specifically drive the expression of dCas9-KRAB in prostate cancer cells, and then designed gRNA to inhibit the expression of PSA. To prevent gRNA from inhibiting the transcription of the PSA promoter on the plasmid, we specially designed the target of gRNA to the ORF region of the PSA gene. This evidence concerns the gene KLK3 and prostate cancer.