To obtain a high-yielding cyclosporin A strain by UV mutagenesis and optimize its fermentation medium formula to increase the production of cyclosporin A.With Beauveria bassiana as the starting strain, the mutagenized strain was obtained by UV mutagenesis, and the single factor experiment was used to investigate the different carbon and nitrogen sources in the fermentation medium of the mutagenized strain.The orthogonal experiment was used to optimize the dosage ratio of the 4 main components in the fermentation culture.The results showed that the mutant high-yield strain CsA-12 was obtained through preliminary screening, rescreening and genetic stability verification.The fermentation medium of the strain was optimized.The optimal carbon source for fermentation was glucose, and the optimal nitrogen source for fermentation was solid corn starch.The optimal fermentation medium formula was glucose 1.6%, solid corn starch 7%, dextrin 14%, and urea 2%, and the pH value was 4.5, which was 55.5% higher than that of the original strain.The results showed that the yield of cyclosporin A could be increased by genetic mutation breeding.