The objective of this study was to figure out the optimal conditions for polyphenol extraction from Polygonum multiflorum Thunb. roots by using pectinase-assisted extraction method. In this research, total phenolic contents (TPC) were determined by the Folin Ciocalteu method and antioxidant capacity (AC) was analyzed by free radical scavenging activity method with Trolox and DPPH as standard reagents. They were described by gallic acid equivalent (GAE) and Trolox equivalent (TE), respectively. The factors from extraction process were studied, gave the highest total phenolic content and strongest antioxidant capacity including material/solvent ratio (1/5-1/13), enzyme concentration (0.1% - 0.5%), extraction time (40 – 120 minutes), pH (3.5 – 5.5) and extraction temperature of (30°C-70°C). The opimal extraction achieved such as the material/solvent 1/11 (w/v), enzyme concentration of 0.2% (v/w), extraction temperature of 50^oC, pH value of 4.5 and extraction time of 80 minutes. TPC and AC peaked at 44.36 mg GAE/g DW (dry weight) and 80.43 μmol TE/g DW. After treatment, the materials were changed strongly and were also observed by scanning electron microscopy (SEM). Some extractive compounds of phenolic such as gallic acid and catechin were determined by HPLC method.