The effects of Nb and Cr addition on the microstructure, corrosion and oxide characteristics of Zr based alloys wereinvestigated. The corrosion tests were performed in a pressurized water reactor simulated-loop system at 360oC. Themicrostructures were examined using OM and TEM, and the oxide properties were characterized by low-angle X-ray diffractionand TEM. The corrosion test results up to 360 days revealed that the corrosion rates were considerably affected by Cr contentbut not Nb content. The corrosion resistance of the Zr-xNb-0.1Sn-yCr quaternary alloys was improved by an increasing Nb/Cr ratio. The crystal structure of the precipitates was affected by a variation of the Nb/Cr ratio. The Zr-Nb beta-enrichedprecipitates were mainly formed in the high Nb/Cr ratio alloy while Zr(NbCr)2 precipitates were frequently observed in the lowNb/Cr ratio alloy. The studies of oxide characteristics revealed that the corrosion resistance was related to the crystal structureof the precipitate.