This study was investigated the residual contents of sulfur dioxide on the 373 kinds of herbal medicine distributed from Korea, China, and Japan. A modified Monier-Williams method was described for the determination of SO2 contents in herbal medicines. The residual contents of SO2 were not detected at 221 products(59.8%) in total 373 products. Regardless of region, SO2 contents were not found at Farfarae Flos, Zizyphi Spinosi Semen, Castanea crenata, and Strychni Ignatii Semen. But it's found at Asparagi Radix, Codonopsitis Radix, Lilii Bulbus, and Kaempferiae Rhizoma of every region collected the samples. Also, SO2 contents were not detected at the herbal medicines which collected cultural fields of dometic. SO2 contents ranged 11~3990 mg/kg(mean 152 mg/kg) at domestic samples, 11~3440 mg/kg(mean 603 mg/kg) at imported samples. After treated with water wash and hot water extraction, the reduction rates of sulfur dioxide were appeared with 24.4%~68.7% and 83.8%~100.0%, respectively. These data will be used to establish a criteron of residual sulfur dioxide in herbal medicines.