For oil well, material analysis on oil well wellhead assembly is an important factor of oil production system life. In order to ensure the long-term development of oil wells, this paper mainly introduces the the material analysis on oil well wellhead assembly,such as material analysis for environment-assisted fracture and stress corrosion on wellhead assembly, requirements for materials of oil well Christmas Tree and tubinghead and so on. By taking T1 well as an example, this paper optimizes the material selection of well wellhead assembly for T1 well. For application, the technology above has a good practicality.