Abstract: The key of determining trace elements in plant by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) is to eliminate the organic matrix effect. In this study, the improvement of acid digesting system, digestion method and sample weight has solved the matrix effect. Digestion results are evaluated by digesting Certified Reference Material (GBW07603) with HNO₃-H₂O₂, HNO₃-HF and HNO₃-HF-H₂O₂. Different sample weights, including 50 mg and 100 mg, and digestion methods including twice-sealed high pressure digestion, once-sealed high pressure digestion and microwave-assisted digestion are evaluated. Trace elements were analyzed by ICP-MS with In as the internal standard element. Experimental results show that HNO₃-HF-H₂O₂ is the best digestion reagent for plants and 50 mg sample has the least matrix effect. The trace element contents for microwave-assisted digestion are obviously lower than the real values. Twice-sealed high pressure digestion was an efficient method for digesting plants.