To study the effects of potassium application on the growth and development of root and root tissue cells， dry matter accumulation of cigar tobacco and economic properties of cigar leaves， and to determine the appropriate potassium application model for local cigar production. Three potassium application modes were set up in the experiment: CK( divided into 1 K application)， T1( divided into 2 K application) and T2( divided into 3 K application). Dynamic changes of root development， dry matter accumulation， root tissue structure and economic properties of cigar tobacco after fermentation grading were analyzed at different periods. The results showed that the root activity of cigar tobacco in all treatments showed an increasing and then decreasing trend with the fertility period， and the dry matter accumulation was gradually increased，and the application of potassium in 2 and 3 times increased the root activity and dry matter accumulation in the middle and late stages of the fertility period of tobacco plants compared with the application of potassium in 1 time. Root volume， root transverse area， mid-column area and number of conduits were smaller in 2 and 3 applications of potassium at 40 d， but the root-crown ratio and root cortex thickness were significantly increased by 9.22% and 38.57% with 2 applications of potassium compared with 1 application of potassium. Root volume and dry matter accumulation were significantly higher in treatments with 2 and 3 potassium applications after 60 d compared with 1 application， and root crowns were smaller. At 80 d， the root transverse area， cortex thickness， mid-column area and the number of conduits were significantly higher in the T1 and T2 treatments than in the 1st application of potassium， and the dry matter accumulation of roots， stems， and leaves was increased by 12.73%， 14.73%， 14.11%， and 15.78%， 23.33%， 17.55%， respectively， in the 2nd and 3rd treatments compared with that in the 1st application of potassium. Both the value of tobacco production and the ratio of cigar wrapper after fermentation grading were highest in the treatment with potassium applied in 3 times as 67000 yuan/hm² and 23.89%， followed by the T1 treatment as 66500 yuan/hm² and 22.88%. In conclusion， divided application of potassium can significantly promote the root development and dry matter accumulation of cigar tobacco， optimize the root tissue structure， and improve the economic benefits of tobacco compared with 1 application of potassium， and the best effect was achieved by 3 applications of potassium，followed by 2 applications of potassium.