The invention relates to a decontamination composition and a decontamination method. The decontamination composition comprises nitric acid with the final volume percentage being 2% to 5%, glycerin with the final volume percentage being 10% to 30%, nitrate with the final concentration being 80 g/L to 140 g/L and oxalate with the final concentration being 5 g/L to 25 g/L. According to the decontamination composition, four components including the nitric acid, the glycerin, the nitrate and the oxalate are reasonably matched and achieve the synergistic effect, and a workpiece to be decontaminatedis smooth without corrosive pitting; generated waste liquid of the decontamination composition does not contain negative ion components such as sulfur, phosphorus and halogen which are harmful to themetal surface of a nuclear facility waste liquid treatment system, and the waste liquid can be directly processed by the nuclear facility waste liquid treatment system.