It is of great significance to achieve a high‐value usage of Chinese medicine residues. This study developed a green ultrasonic cell grinder extraction (UCGE) method has been developed for cyperenoic acid extraction from water decocted Crotonis Crassifolii Radix. The response surface methodology was introduced for the experimental design. The optimum conditions were as follows: 52 % ethanol concentration, 28 : 1 mL/g ratio of solution‐to‐solid, 500 W extraction power, and 28 min extraction time. Anti‐inflammatory test was performed to investigate the medicinal uses of the extract from the herb residue. The microstructure of the extracted samples was also investigated using scanning electron microscopy to understand the extraction mechanism. A higher extraction yield of 1.016 mg/g and better anti‐inflammatory activity were obtained under UCGE compared to a conventional solvent extraction. Meanwhile, the sample structure was seriously damaged by UCGE. The results show that UCGE is a promising green and efficient technology for extracting functional components, and has great potential in recycling waste resources.