氧化镁是水泥中要求准确测定的主要物质之一。利用激光诱导击穿光谱(LIBS)技术对普通硅酸盐水泥样品进行了等离子体光谱分析。选择Mg I 517.2 nm特征谱线作为分析线，测量了不同激光能量下的光谱信号强度以及对应的信噪比，确定了最佳激光能量为40 mJ。为减小实验误差，将Mg 517.2 nm的光谱强度和516~520 nm的光谱强度积分之比作为内标，建立了MgO质量分数测定的定标曲线，定标曲线的线性系数达到了0.9959。采用循环反演的方法检测了MgO定量分析的测量精度，最大相对偏差和平均相对偏差分别为5.9%和2.48%，LIBS对水泥样品中的MgO质量分数的检测限达到了0.51%。

MgO is one of the main substances which are required to be accurately determinated in cement. The plasma spectra of ordinary silicate cement obtained by laser-induced breakdown spectroscopy (LIBS) are analyzed. Mg I 517.2 nm characteristic line is selected as the analysis line. By measuring the spectral intensities of the signals and the corresponding signal-to-noise ratios with different laser energies. It′s found that the optimal energy is 40 mJ. In order to reduce the error, the ratio of the spectral line intensity of Mg 517.2 nm and the spectral integral from 516 nm to 520 nm is used as internal standard to establish the MgO mass fraction calibration curve. The carrelation coefficient of calibration curve is 0.9959. Cycle inversion method is used to detect the accuracy of MgO quantitative analysis. The maximum relative error and the mean relative error are 5.9% and 2.48%. The detection limit of MgO mass fraction in cement obtained by LIBS is 0.51%.