Background: Cimicifugae rhizoma was a Ranunculaceae herb belonging to the composite family, and the roots of C. rhizoma have been widely used in tradition Chinese medicine. Materials and Methods: Ultrasound-assisted extraction (UAE) of phenolic compounds from C. rhizoma. Caffeic acid (CA), isoferulic acid (IA), ferulic acid (FA), and total phenols were quantified by high-performance liquid chromatography-diode array detection and ultraviolet-visible spectrophotometer. Effects of several experimental parameters, such as ultrasonic power (W), extraction temperature (°C), and ethanol concentration (%) on extraction efficiencies of phenolic compounds from C. rhizoma were evaluated. Results: The results showed that the optimal UAE condition was obtained with ultrasonic power of 377.35 W, extraction temperature of 70°C, and ethanol concentration of 58.37% for total phenols, and ultrasonic power of 318.28 W, extraction temperature of 59.65°C, and ethanol concentration of 64.43% for combination of CA, IA, FA. Conclusions: The experimental values under optimal conditions were in good consistent with the predicted values, which suggested UAE is more efficient for the extraction of phenolic compounds from plant materials.