The structural elucidation of the main constituents in enzymatically hydrolyzed coix extract, a natural food preservative, was carried out. After peracetylation, five compounds, namely peracetylated forms of glucose, maltose, maltotriose, maltotetraose, and maltopentaose were isolated. The structures were determined by PFG HMQC and HMBC experiments. In addition, by using HPLC with an RI detector, the main components of this coix extract were identified as a mixture of oligosaccharides having one to seven glucose units coupled through alpha-(1-->4) linkages. Since this extract showed no antimicrobial activity, its preservative effect may be caused by its covering of the food surface, thereby blocking contact with air.