In quantitative analysis by laser-induced breakdown spectroscopy (LIBS), it is necessary to take account of self-absorption effects on emission line intensity. In this work, a fiber laser ablation LIBS (FLA-LIBS) system was developed to reduce the self-absorption effects and improve the quality of quantitative analysis. The self-absorption degree was estimated for Mg and Ca lines, and a comparison of the calibration curves using LIBS and FLA-LIBS was carried out. The coefficients of determination (R²s) of linear calibration curves of Mg and Ca increased from 0.841 and 0.847 in conventional LIBS to 0.954 and 0.859 in FLA-LIBS, respectively. The self-absorption coefficients of Mg and Ca in FLA-LIBS were larger than those in conventional LIBS. And the ratios of Mg and Ca doublet intensity in FLA-LIBS were closer to theoretical values. These results show the great potential of FLA-LIBS in reducing self-absorption effects, especially for high concentration elements.