Abstract: The relationship between soil moisture content and the contents of K, Ca and Mg in tobacco leaves was experimented with cinnamon soil and brown soil in pots.The results showed that the contents of K and Ca in tobacco leaves grown in the two soils and Mg content in leaves grown in cinnamon soil increased while the tobacco was under moderate stress of water at middle stage and enough irrigated at later stage.Ca and Mg contents were higher in tobacco leaves in soil with low moisture content, it might be(related) with the exchange between mineral cations in soil solution and the competition for the absorptive points of roots. The content of K was negatively correlated to Ca and Mg contents by and large, Ca content was positively correlated to Mg content.Regression analysis indicated that the four factors: Mg and Ca contents in tobacco leaves, soil's moisture contents in 30-60 and 61-90 days after transplant(W1 and W2), affected K content in tobacco leaves differently in degree, Mg > Ca > W2 in cinnamon soil and Ca > W1 in brown soil.