Abstract: Determining arsenic in tungsten and molybdenum ores using Hydride Generation-Atomic Fluorescence Spectrometry (HG-AFS) without separation and a screening agent commonly suffer from the interferences of associated elements such as W, Mo, Cu, Pb, Zn, Bi and Cd. In this study, the samples were digested by hydrochloric acid-nitric acid (volume ratio of 5 : 1) in a water bath. Citric acid and potassium iodide solution were used to screen interferences of associated elements by reducing these elements to low valences or forming the precipitates. Lastly thiourea-ascorbic acid solution was added and As content was determined directly by HG-AFS. The method yields an As detection limit of 0.014 μg/g, precision of 0.7%-7.5%, and recovery of 92.3%-102.9%. Compared to the national standard method, this method has the advantages of low detection limit, wide detection ranges, and direct determination without separating interference elements.