The invention discloses a metallographic etching solution for expansion alloy. The metallographic etching solution comprises 1.0%-1.2% of ferric trichloride, 23.0%-28.7% of concentrated hydrochloric acid, 27.3%-34.1% of concentrated nitric acid and 36.0%-48.7% of distilled water. According to the metallographic etching solution for the expansion alloy, different detects in metallurgical structuresand structures of metallographic samples etched by the etching solution can be observed clearly, and the crystal boundary is clear; and the contrast is obvious, in favor of optimizing the productiontechnology and improving the product quality.