Abstract: To efficiently remove lignin components abundant in tobacco processing by-products (stems) and achieve its high-value utilization, a synergistic treatment process combining hydrothermal pretreatment (HTP) with a ternary deep eutectic solvent (DES) composed of choline chloride (ChCl), lactic acid (LA), and ethylene glycol (EG) was used. The effects of single HTP, single DES, and the combined HTP-DES process on lignin removal effect and component separation selectivity were systematically compared. The results showed that: 1) Under synergistic HTP (100 ℃, 1 h) and DES (100 ℃, 4 h) treatment, the maximum lignin removal rate reached 76.27%, which was significantly higher than that of the single DES treatment (100 ℃, 4 h; 57.71%), and the cellulose retention rate was more than 90.00%, indicating good component separation selectivity. 2) Hydrothermal pretreatment effectively destroyed the structure of the lignin-carbohydrate complex (LCC), promoting dissolution of lignin in DES. After DES was reused five times, the lignin removal rate remained above 60.00%, demonstrating the good recycling stability and economy. 3) The regenerated lignin exhibited a low molecular weight and a intact structure.