Pot experiment for studying the status of K nutrition of tobacco plants was carried out in 1995 and 1996 by liming or adding FeSO₄ or sulfur powder to regulate the pH value of soils.The main results obtained are as follows:The average yield of tobacco leaves is higher in the soils with pH 5.33 or 6.1,but that is lower in the soils with pH above 6.1 or below 5.0.The absorbing capacity of potassium by tobacco plants and the efficiency of potassium fertilizer are highest in the soils with average pH 5.33,below or above this pH value the two indexes are lower.According to the study it is shown that the desirable yield of tobacco leaves with K content about 3.3% can be expected if tobacco is planted in soils with pH 5.33~6.1 range and N,P and K fertilizers is fully supplied.It is pointed out tentatively that soil pH 5.0 is a critical value that tobacco plants were injured by active Al.