Abstract: 【Objective】 The purpose of the study was to study the effects of Priestia megaterium on the yield and quality of different varieties of black-leaf Chinese cabbage, and to provide theoretical basis for promoting the application of beneficial bacteria.【Method】 Four black-leaf Chinese cabbage varieties were used, and three inoculation levels of P. megaterium(3, 6 and 9 kg/ha) were set, with no inoculation as control(CK). Variance analysis and principal component analysis were used to analyze the effects of P. megaterium on the yield, nitrate content, free amino acid content, soluble protein content, vitamin C content and soluble sugar content of black-leaf Chinese cabbage.【Result】 With the increase of P. megaterium inoculation amount, nitrate content of all varieties of black-leaf Chinese cabbage showed a trend of decreasing and then increasing, with the maximum decrease of 72.5% compared with CK. The free amino acid content and vitamin C content showed a trend of increasing and then decreasing, with the maximum increases of 79.13% and 8.91% respectively compared with CK. With the increase of P. megaterium inoculation amount, yield of No. 8210 and A321, soluble protein content of Tiancui 331, soluble sugar content of Tiancui 331 and Tiancui 326 all showed an overall trend of increasing and then decreasing, with the maximum increases of 28.08%, 5.25% and 19.60% respectively compared with CK. The soluble protein content in No.8210 and soluble sugar content in A321 showed an overall trend of decreasing and then increasing, with the maximum decreases of 10.20% and 10.42% respectively compared with CK. The two factors, P. megaterium inoculation amount and black-leaf Chinese cabbage variety, had extremely significant interaction effects on reducing nitrate content and increasing free amino acid content, vitamin C content and soluble sugar content (P<0.01). Principal component analysis revealed that the optimal inoculation amount for No.8210 and A321 Chinese cabbage was 6 kg/ha, and the amount for Tiancui 331 and Tiancui 326 was 3 kg/ha.【Conclusion】 Inoculation with P. megaterium improves the quality of black-leaf Chinese cabbage by decreasing nitrate content and increasing free amino acid, vitamin C and soluble sugar while increasing its yield. In addition, the variety of leaf vegetables significantly affects the inoculation effects of P. megaterium on the yield and quality of black-leaf Chinese cabbage.