Taking advantage of the interaction between potassium dihydrogen phosphate combined with boron，zinc and molybdenum is an important measure for high yield and high efficient of nutrients for flue-cured tobacco.Seven treatments were set up，including no foliar fertilizer(CK)，foliar boron(B)，foliar zinc(Zn)，foliar molybdenum(Mo)，foliar potassium dihydrogen phosphate+boron(KH2PO4+B)，foliar potassium dihydrogen phosphate+zinc(KH2PO4+Zn)，foliar potassium dihydrogen phosphate+molybdenum(KH2PO4+Mo).The effects of potassium dihydrogen phosphate combined with boron，zinc and molybdenum nutrient content，physiological indicators and chemical composition of flue-cured tobacco leaves were explored.The results showed that，compared with CK treatment，the application of microelements alone increased plant height，girth，leaf area，the soluble sugar and protein content，superoxide dismutase activity, catalase activity, peroxidase activity and net photosynthetic rate，yield of flue-cured tobacco leaves by 3.9%-6.7%，5.1%-11.8%，9.2%-38.2%，9.6%-16.7%，7.1%-18.2%，7.9%-18.2%，6.0%-16.3%，11.1%-17.1%，7.3%-18.0%，0.3%-14.6%，respectively.The single spraying of boron，zinc，and molybdenum demonstrated optimal effects on leaf nitrogen，phosphorus，soluble protein，chlorophyll content，net photosynthetic rate，as well as yield，output value，and the proportion of high-grade tobacco leaves in flue-cured tobacco.These parameters exhibited a gradually increasing trend from boron to zinc to molybdenum.Plant height，number of blades，girth，the soluble sugar and protein content，catalase activity, peroxidase activity，malondialdehyde content，net photosynthetic rate and yield of flue-cured tobacco treated with potassium dihydrogen phosphate combined with trace element spraying were increased by 4.5%-18.6%，4.7%-17.7%，3.7%-17.3%，7.0%-9.9%，18.3%-39.7%，15.7%-40.5%，12.7%-38.8%，3.7%-5.8%，4.8%-16.7% and 5.8%-12.9%，respectively，compared to the treatment with trace element spraying alone.The chemical composition of flue-cured tobacco was optimized.The combined application of potassium dihydrogen phosphate with molybdenum significantly increased potassium content in upper leaves by 10.4% and 6.3%，compared to boron and zinc，respectively.Comprehensive analysis indicated that single molybdenum spraying demonstrated superior effectiveness to individual boron or zinc application，and the combination of potassium dihydrogen phosphate with molybdenum demonstrated superior effectiveness to the combination of potassium dihydrogen phosphate with boron or zinc application.