Potassium (K⁺), as one of the most important nutrient elements, plays important roles in tobacco production, such as stress resistance and improvement of leaf combustibility and quality. After topping or during drought stress, K⁺ usually outflows from tobacco, which has negative impacts on tobacco production. So, it is necessary and valuable to study the control of the K⁺ outflow from tobacco. The objective of this study was to explore the effects of salicylic acid (SA) on the K⁺ outflow from tobacco. Different concentrations and application methods of SA were adopted, and the K⁺ content in tobacco leaf or roots culture solution were analysed before and after topping. Then, the RNAi lines with the knockout of gene TORK1, the only one known K⁺ efflux channel in tobacco, were used to verify the effects of SA. The results showed that topping led to the increase of K⁺ outflow from tobacco roots and decreased the K⁺ content in different leaf positions. Five µM or 50 µM SA applied to culture solution could inhibit the K⁺ outflow, while 500 µM SA had opposite effects. Additionally, the reduction of leaf K⁺ could be alleviated when placing a cotton ball saturated with 5 µM SA onto the topped area, but SA injection into the vein had no distinguishable effect. The gene expression of TORK1 was significantly inhibited in the RNAi lines by 5 µM Estrogen, and was further inhibited by adding 50 µM SA into the culture solution. As TORK1 expression decreased, the K⁺ content also decreased. However, there was no obvious effects of 500 µM SA on gene expression and K⁺ content. In conclusion, SA regulates the tobacco K⁺ outflow through the TORK1 channel. These results provide an original foundation for future applications of SA to tobacco.