This study compared the effects of three kinds of fertilization depth on movements of potassium ions and tobacco leaf quality in plastic film planting pattern. The project was T1 (fertilization depth was 10 cm), T2 (fertilization depth was 20 cm) and T3 (fertilization depth was 30 cm). We took soil samples with aluminium boxes in the cross sections of the ridges and sampling sites were: T1: 0~5, 15~20, 25~30, 35~40 cm; T2: 0~5, 10~15, 25~30, 35~40 cm; T3: 0~5, 10~15, 20~25, 35~40 cm. Sampling was done five times. We measured water soluble potassium and exchangeable potassium in the soil; potassium, calcium and magnesium concentrations of roots, stems and leaves were measured; ingredients and quality of tobacco sample were scored. The results suggested that fertilizing depth influenced movement direction and translocation quantity of potassium ions. Potassium ions mainly transferred vertically upwards and downwards. When fertilizing depth was less, potassium ions mainly moved upwards. When fertilizing depth increased, up-movement was replaced by down-movement. Fertilizing depth influenced distribution of potassium ions in the soil. When fertilizing depth was improved, the distribution depth of potassium increased. The fertilization depth of 20 cm was propitious to assimilation. But, when considering the ratio of K/(Ca+Mg), we found T3>T2>T1. Tobacco leaves of T3 had the most harmonious ingredients and the best quality. The quality and quantity of aroma of T3 were enhanced, and the aftertaste of T3 tobacco leaves was pleasing.