Copper and zinc were determined in MSW samples collected from Tianziling landfill site in Hangzhou, Zhejiang, east China by modified BCR sequential extractions. Three pretreatment methods, including fresh, air drying, and oven drying, were studied. It showed that the main cause of fraction transfer after drying could be ascribed to the variation of sample status, including the evaporation of ammonia nitrogen and volatile fatty acid (VFA), the shift of sample pH, and the oxidation of sulfur, when contacted with atmospheric oxygen or exposed in high temperature during drying processes. Effect of sample pretreatment methods on speciation of copper and zinc in MSW concluded that oven drying should not be used because the changes are more numerous and generally of greater amplitude, air drying was a 'neutral' treatment relatively, while fresh sample might be the best choice if possible. To validate the effect and determine the source of pretreatment methods clearly, certified reference materials of MSW should be confirmed in the future research.