In order to understand the residual SO2 of dehydrated Day Lily from producing farm, a total of 63 samples, including 31 samples processed in 1999 and 32 samples processed in 2000, were purchased from traditional and super markets in Hualien and Taitung in February and October of 2000 respectively. These samples were analyzed by using the method, the sulfur dioxide test published by Department of Health, Executive Yuan, R.O.C. in 1983, to detect the bleaching agents in food. The results showed that only 2 samples (6.5%) processed in 1999 and 5 samples (15.6%) processed in 2000 met the hygienic standard for bleaching agents in dehydrated Day Lily.