For the laser-induced breakdown spectroscopy (LIBS) for steel liquid online quantitative analysis, due to the influence of matrix effect, the precision is seriously affected, therefore in the quantitative analysis we should try to reduce the influence of the matrix effect on the elements under tests. Internal standard method is the most common method of LIBS quantitative analysis. This method can partially eliminate the matrix effect in measurement process, but it can only be applied to samples with a simple elemental composition, and for complex samples it cannot effectively correct the matrix effect. By adopting the general matrix correction method, real-time online quantitative analysis of molten steel cannot be realized and the following data processing will be difficult, so this method is not suitable for field tests. We use the improved linear regression equation in the matrix correction method in combination with the Mathematica brief calculation program. It can effectively work for the matrix correction of LIBS steel liquid online quantitative analysis. Experiment verifies the feasibility of this method.