<p> <?tk 4?>A lot of hawthorn leaves are treated as agricultural and forestry wastes. In fact, there are many polyphenols and flavonoids with high biological activity in hawthorn leaves. Ultrasonic-assisted extraction (UAE) of phenolic antioxidants from Hawthorn leaves was studied using deep eutectic solvents (DESs). Multiple DESs were prepared and the extraction efficacies of them were evaluated. Choline chloride-ethylene glycol-based DES (ChCl-EthG) was chosen as the optimal extractant based on the extraction yield, cost of solvent, and difficulty of post-treatment. The extraction process was optimized by response surface method (RSM). The analysis of variance (ANOVA) showed that ultrasonic time, power, temperature, and solvent water content had significant effects on the antioxidant capacity of the extract. Under optimal conditions, the experimental ferric reducing antioxidant power (FRAP), total polyphenol (TPC) and total flavonoid (TFC) content of extract agreed with the predicted results with relative deviation less than 4.49%. The above three indexes were noticeably greater than those of extracts from conventional solvents including water, ethanol, and n-butanol. The result can be explained by that the predicted solubility of main antioxidants rutin and ferulic acid from Hawthorn leaves in ChCl-EthG using Cosmoquick is higher than that in conventional solvents. Moreover, SEM analysis showed that more pores and cracks were observed on the surface of the hawthorn leaf cells after ChCl-EthG treatment, which benefit for the release of antioxidants.<?tk 0?></p>