An efficient route to prepare l-glucose and l-galactose is described. The l-sugars are achieved by using the strategy of switching the functional groups at C1 and C5 of d-glucose and d-mannose. The oxidation and reduction of the silyl enol ether at C1 and the lead(IV) tetraacetate mediated oxidative decarboxylation at C5 are the key steps. l-Glucose and l-galactose are prepared in a convenient and inexpensive way.An efficient route to prepare l-glucose and l-galactose derivatives by using the strategy of switching the functional groups at C1 and C5 of d-glucose and d-mannose, respectively, was developed. l-Sugars could be prepared on a large scale by this strategy with high overall yields.