The goal of this study is to examine the infl uence of type of solvent (acetone, ethanol, methanol, and water), raw solvent/material ratio (20/1–60/1, v/w), solvent concentration (30–80%, v/v), temperature (30–70°C), time of extraction (10-30 mins) and power consumption of 550 W on the extraction yield of total phenolic compounds (TPC) and antioxidant activity (AC) from Polygonum multiflorum Thunb. roots. TPC and AC were determined by the Folin–Ciocalteu assay and DPPH assay. The optimal conditions for extraction process were 60% acetone-water mixture as solvent, solvent/material ratio of 30/1, extraction temperature of 60°C and extraction time of 15 mins. TPC and AC obtained were approximate 43.28±0.54 mg GAE/g DW (Dry weight) and 343.88±3.06 μmol TE/g DW, respectively. The effect of ultrasound-assisted extraction (UAE) on structure of materials of Polygonum multiflorum Thunb. root was observed by scanning electron microscopy (SEM). HPLC method was employed to determinate some main phenolic compounds including catechin, gallic acid, and resveratrol.