The invention discloses a material outer surface coating layer for a nuclear reactor. The coating layer is deposited on the outer surface of a matrix material used in the nuclear reactor and sequentially comprises a Zr-Cr or Ti-Cr transition layer, a Cr deposition layer and a CrN hardening layer from inside to outside. The preparation method of the coating layer adopts a physical vapor depositionmethod, a thermal spraying method, a cold spraying method, a laser cladding method, an electroplating method or a chemical vapor deposition method, and arc ion plating in the physical vapor depositionmethod is preferred. The cladding material obtained by coating the coating layer on the zirconium alloy matrix material has good properties of high temperature oxidation resistance, corrosion resistance, membrane-based collaborative deformation and abrasion resistance and is a kind of accident-resistant nuclear fuel cladding materials with development prospects, and the coating cladding materialbased on an N36 alloy has better mechanical properties at high temperature.