Abstract:The sample pretreatment methods in determination of heavy metal were considered as the key step in the analysis process，and it's were proved directly related to the precision and reproducibility.Through the analysis on the existing forms of cadmium and arsenic in foods and the processing of enzyme-pretreatment，the application of enzyme in sample-pretreatment was discussed in this paper.The conclusions were as follows：cadmium was mostly bonded with protein in foods，and the NaCl extract form was the most in leaf vegetables，but the acid extract form was the most in corn and sorghum；arsenic was mostly exist as organic-form in meat and cereals，and methanol was usually used as extracting agent，but inorganic arsenic was the most in vegetables，and acid was used as extracting agent.The sample size，enzyme type，enzyme concentration，pH，temperature，the ratio of liquid and solid and the time of pretreatment were the influences of enzymepretreatment.