Abstract: Two field trials were conducted to study the potassium content of exudation of tobacco sap.In the first trial, 57 tobacco genotypes of different types were grown under uniform soil treatment that was given of 90kgN/ha with P and K added such as the ratio N:P₂O₅:K₂O=1:2:3.In the second trail, 20 flue-cured tobacco genotypes were grown under 3 treatments of soil-applied K+ in which the N application was always 90kg/ha, but the ratios of N:P₂O₅:K₂O were L=1:2:0, S=1:2:3, and H=1:2:5.The results showed that the potassium contents of exudation of tobacco sap were as following:Nicotiana rustica > cigar > burley tobacco > flue-cured tobacco > oriental tobacco > local sun-air-cured tobacco > Maryland tobacco.There was little difference in the potassium content of exudation of tobacco sap between the levels of applied potassium and genotypes.The effects of genotypes on the levels of applied potassium appeared to be different.There was significant positive correlation between the exudation of sap and the potassium applied.