Abstract: To investigate the extraction effect of total flavonoids from Crataegus pinnatifida by using ultrasonic-assisted deep eutectic solvents, and optimize the extraction parameters. Firstly, ten kinds of deep eutectic solvents (DESs) composed with different components were prepared for extracting total flavonoids of C. pinnatifida, and the DESs with the highest yield were selected. Then, water content and the proportion of each component contained in DESs were screened on the basis of the single factor experiments. Meanwhile, the response surface methodology (RSM) was employed to optimize extraction temperature, liquid-solid ratio and ultrasonic time, and obtain the extraction parameters. As results, glycerol/choline chloride (molar ratio 3:1) DESs containing 50% water was chosen as the optimal extraction solvent, and the optimum extraction parameters were as follow: Ultrasonic time (21 min), liquid-solid ratio (42 mL/g) and extraction temperature (72 ℃). Under the above extraction condition, the yield of total flavonoids, rutin, vitexin, hyperoside, quercetin in DESs extract were 7.72%, 0.24%, 0.33%, 0.18% and 0.27%, respectively, which were superior to the traditional alcohol extraction method. The DPPH radical scavenging rate of DESs extract at 0.1 mg/mL was 86%. Compared with methanol extract, the antioxidant activity of DESs extract was enhanced. Therefore, ultrasonic-assisted deep eutectic solvents extraction method could effectively improve the yield of total flavonoids from C. pinnatifida, and would provide the scientific evidence for the resource development and utilization of C. pinnatifida.