Gene therapy refers to transfer a normal exogenous gene into a target cell to correct or compensate the diseases caused by gene defects and abnormal expression in achieving therapeutic purposes. Broadly speaking, gene therapy also includes measures and new technologies for treating certain diseases at the DNA level. Traditional gene therapy generally uses a harmless virus or other vectors to copy normal genes into cells to replace the disease-causing defect genes. The CRISPR technology corrects defective genes by excising damaged DNA and replacing it with the correct gene sequence directly. This method eliminates the risk of inserting a exogenous gene into the wrong position and activating the oncogene. The corrected gene is still regulated by the promoter of the gene itself, so the protein in the cell will maintain normal level. The development and maturity of CRISPR technology has opened up new ideas and new methods for gene therapy of a large variety of diseases.