Abstract: To develop a high-temperature inelastic constitutive model suitable for structural integrity assessment, the high temperature mechanical properties of 316 austenitic stainless steel and 9Cr-1Mo steel are reviewed in this paper. By comparing the uniaxial tensile, strain-controlled cyclic, creep and plastic-creep interaction properties, the similarities and differences of the high-temperature mechanical behaviors of the two types of nuclear steels are demonstrated. Also, temperature, loading rate, stress level etc. have an influence on the above mentioned mechanical properties. In addition, two types of high-temperature constitutive models are comprehensively evaluated, and the development trend of models is discussed. The comprehensive description of the high-temperature mechanical properties of nuclear steel is helpful for the complete evaluation of nuclear reactor structure.