Abstract: The sample was decomposed with hydrochloric acid-nitric acid-hydrofluoric acid-perchloric acid. Then, the content of CaO、MgO in cement limestone was simultaneously determined using inductively coupled plasma atomic emission spectrometry(ICP-AES). According to the properties of CaO and MgO, different series of standard solutions were prepared, and the best analytical lines for the elements were determined. The correlation coefficients of calibration curves of CaO and MgO were 0.999 9 and 0.999 5 respectively. The detection limit was 0.009 0% and 0.004 0%, respectively. The limestone standard sample was used for the precision test, the relative standard deviations (RSD, n=12) of CaO and MgO were 0.12% and 2.87%, respectively. The proposed method was applied to the determination of certified reference material and real samples of limestone, and the results were basically consistent with the certified values of certified reference material or the X-ray fluorescence(XRF) value of the actual sample.