It is known that Ni based alloy suffered SCC in primary water of PWR. It has been clarified that the SCC crack growth rate of weld metal is faster than that of base metal of alloy 600(UNS N06600) and the SCC cracks hardly propagate in both weld and base metal of alloy 690(UNS N06690). In this study, four base metals and two weld metals of alloy 600 and one base metal and two weld metals of alloy 690 have been examined to clarify the metallurgical factors which affect on the SCC propagation behavior. The followings are clarified the metallurgical factors which possibly affect on the SCC propagation behavior of Ni based alloys.