Abstract: An optical fibre,self-pressure-controlled,hermetic micro-wave heating system was used for aicd-digestion of agricultural samples,such as soil and plants,for the determination of heavy metals in such samples.Various factors influential to the efficiency of sample digestion,including the acids used for the digestion,parameters and conditions of micro-wave heating,methods necessary for pretreatment of sample and etc,were studied and optimized.As compared with the wet digestion of sample under normal pressure,the method described in this paper had the distinguishing features of less time required for digestion of sample,much smaller amounts of acid or solvent required for digestion of sample,less contamination with the sample,thus leading to more precise and accurate analytical results.