Abstract: A new method for corrosion of GH4169 alloy was introduced. When the metallographic examination of the alloy sample corroded by the new method was carried out, only the austenite grain boundary could be displayed, and the δ phase was not displayed. The microstructure of the material was observed by optical microscope, and the grain size was counted by cut-off point method. The results show that there was no deposition film on the surface of the sample corroded by the new method, and the microstructure was clear. This method was suitable for the grain size test of GH4169 alloy.