Abstract: This study aimed to optimise the ultrasound-assisted deep eutectic solvent extraction of Cerasus humilis proanthocyanidin (CPC) and to compare it with the traditional 70% ethanol extraction method, focusing on the assessment of the structural composition and biological activity of the purified materials. The extraction process for ultrasound-assisted deep eutectic solvent extraction of CPC was optimised using single-factor combined response surface methodology, the average degree of polymerisation was determined after purification, and the functional groups and composition of CPC were analysed qualitatively by Fourier infrared spectroscopy and high performance liquid tandem mass spectrometry (UPLC-OE-MS/MS). The effects of temperature, light, metal ions and pH on the stability of CPC were explored, and the antioxidant capacity of CPC was assessed with the help of DPPH, ABTS⁺ free radical scavenging assay and FRAP method, and the in vitro hypoglycaemic activity of CPC was investigated by α-amylase and α-glucosidase inhibition assays. The results showed that choline chloride-1,2 propanediol (molar ratio 2:1) was screened as the extraction solvent, and the yield of CPC was 21.11%±0.10%, which was 1.5 times higher than that of 70% ethanol extraction, at 40% (V/V) water content, 1:20 (g/mL) material-liquid ratio, 49 ℃ ultrasonication temperature, and 49 min extraction time. The purified purity of DES-extracted CPC was 87.41%±2.54%, and the average degree of polymerisation was 3.09±0.02. CPC was based on protocyanin as the main structural unit and oligomeric protocyanidins as the main components. The retention rate of CPC was more than 85% after 10 h at 20 ℃ protected from light, however, the stability was significantly reduced under high temperature, alkaline and light conditions, and it was greatly damaged by metal ions Fe³⁺, Fe²⁺ and Cu²⁺. In addition, CPC showed strong antioxidant properties and hypoglycemic activity in vitro. In conclusion, the ultrasound-assisted deep eutectic solvent extraction method not only significantly improved the extraction yield and purity of CPC, but also performed excellently in maintaining its bioactivity, which provided an important theoretical basis for the green extraction and application of functional active substances in Cerasus humilis.