Abstract: In order to study the influence and mechanism of applying different root-promoting agents on the growth, development and quality of tobacco plants, experiments were conducted to analyze the effects of applying Yiweiyuan organic water-soluble fertilizer (T1), mineral potassium fulvic acid (T2), carbon adsorption polyglutamate (T3) and Fugenduo root-promoting agents (T4) on the growth and development of tobacco roots and the yield and quality of upper leaves, with no root-promoting agent treatment as the control (CK). The results showed that compared with CK, the application of the root-promoting agents increased the root volume of primary, secondary and tertiary modules of tobacco plants by 75.2%-120.5%, 50.4%-75.0% and 50.2%-96.5%, respectively. The root vigor of primary and secondary modules also increased significantly. The SPAD values of upper leaves under T1, T2, and T3 treatments increased, and the average daily rate of change of SPAD for upper leaves during the maturing stage decreased. Application of the root-promoting agents increased the total sugar content of tobacco upper leaves. T2 and T3 treatments significantly decreased the nicotine content of tobacco leaves. The application of the root-promoting agents increased the yield, production value and net income of cured upper tobacco leaves by 3.7%-7.2%, 6.8%-10.6% and 1 644-4 558.5 RMB Yuan/ha, respectively. Among them, T3 treatment had the largest growth rate. Therefore, the application of carbon adsorption polyglutamate as a root-promoting agent can improve the development and vigor of root, ripening holding ability of upper leaves and quality of tobacco leaves.