Abstract: The methods of water bath dissolution by aqua regia to open dissolution by acid mixing HCl-HNO₃-HF-HClO₄ and determine Fe, Cu and S in pyrite and chalcopyrite by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) are discussed in this paper. By applying a weighting method to prepare standard solutions, the error caused by scale reading can be greatly reduced during the dilution step. The advantages of using the water bath dissolution by aqua regia method include reduced digestion time, reduced amount of reagent addition and simple analytical processing. When Fe combines with Si in sulfide ore, it cannot be dissolved by aqua regia, yet it can when using open dissolution by acid mixing. The optimal spectrum lines were selected to determine high concentration of Fe, Cu and S (x%-xx%) with dilution factor of 1000. Both sample preparation methods are simple to operate and attain good accuracy and precision. The method was validated by the national standard materials of GBW 07267 (pyrite) and GBW 07268 (chalcopyrite). The accuracy (RE) and precision (RSD, n=5) of Fe and Cu were less than 2%. However, accuracy and precision for S was lower when using the method of open dissolution by acid mixing, yielding a RE and RSD of -9.48% and -18%, respectively. The short period stability of GBW 07267 and GBW 07268 was tested by 10 continuous determinations using the method of water bath dissolution with aqua regia; the RSD being less than 2.