A thermal-analysis-based output stabilization method and system for improving 3D printing output reliability are provided. The thermal-analysis-based output stabilization method according to an embodiment of the present invention comprises steps in which: an output stabilization system performs first stacking thermal analysis on a plurality of residual heat quantity review specimens for which a process range corresponding to normal output quality is set; the output stabilization system performs second stacking thermal analysis on an actual stacked product on the basis of the first stacking thermal analysis result in the same manner as the first stacking thermal analysis method; and the output stabilization system performs stability review on the stacking result of the stacked product on the basis of the second stacking thermal analysis result.