Abstract: The study is made of large numbers of dispersion indication discovered in the fluorescent penetrating inspection of DD5 single crystal super alloy blade. And the substance of indication is validated in the microstructure analysis method. Meanwhile, the relation of size is quantitatively analyzed between original defect and indication. The result of study indicates that the dispersion indications discovered in the fluorescent penetrating inspection of DD5 single crystal super alloy blade are caused by erode treatment. The reference data of study is supplied for the production of crystal super alloy blade and indication evaluation.