为实现激光诱导击穿光谱(LIBS)分析精密度的改善，研究了一种基于分析谱线和内标谱线相关性的内标谱线选择方法。对相关谱线内标法的方法原理进行了理论分析和数值计算，并采用微合金钢标样LIBS 谱线Co I 350.23 nm和Cr I 427.48 nm 进行了实验验证。结果表明，要使得LIBS 谱线分析精密度得到改善，必须同时满足分析谱线和内标谱线的相关系数γ >0.5、噪声正比因子b>0.5 及γb > 0.5 的条件。精密度的改善倍数R 随γ 和b 的增加而增大，但当在γ >0.5 后，R 随b 先增大后减小，b=1 时达到最大值，即当分析谱线的波动大于内标谱线的波动时，相关谱线内标法的调节能力逐渐减弱。

To improve the analytical precision of laser-induced breakdown spectroscopy (LIBS), a modified internal standard approach is studied based on the correlation of analytical lines and reference lines. The approach is investigated in detail by principle analysis and numerical calculation firstly, then experimental verification is carried out using the analytical lines of Co I 350.23 nm and Cr I 427.48 nm from the micro-alloy steel standard samples. The results show that, to improve the analytical precision of LIBS, it must meet the necessary conditions that the correlation coefficient of analytical line and reference line γ >0.5, the noise proportional factor b>0.5, and γb > 0.5 . The precision enhancement factor R increases with the increasing of γ , but increases first then decrease with b. When the fluctuation of analytical lines is greater than that of reference lines, the degree of precision improvement decrease gradually.