Abstract: In the present work,the nodular corrosion properties in the steam（500 oC/ 10.3 MPa） of N18 zirconium alloys after different heat treatment were investigated.The nodular corrosion of N18 alloys was liable to occur after α +β binary phases at 780oC and α uniary phase treatment at 700oC.Microstructure ob-servation found that the dilution of alloying element（especially Nb） at high temperature contributed the dete-rioration of nodular resistance.Furthermore,the formed alloying elements depleted zone could not be elimi-nated effectively by large deformation or low-temperature annealing treatment.A sufficient solution treat-ment at β phases has been proved as an effective way to eliminate the alloying elements depleted zone.