In order to investigate high temperature mechanical properties and fracture behaviors of Mone1-400 alloy and cladding metal tensile tests were conducted at different temperatures on a Gleeble-1500D thermal simulation machine. The results show that strength of base metal and cladding metal are declining from 700℃ to 1100℃. The plasticity of base metal increases with increasing temperature, while plasticity of the cladding metal declines. At 700℃, the dispersed second phase particles has played a significant role in strengthening the yield strength and tensile strength on the cladding metal, while plasticity of which is seriously deteriorated. At the range of 700 - 1100℃, the fracture pattern of base metal is ductile fracture, while fracture pattern of cladding metal from ductile fracture gradually become brittle fracture. In the actual thermal processing and application, it is crucial to avoid cladding metal large deformation to prevent thermal cracking, and the base metal should not be used above 700℃.