Abstract: Mechanical properties and structure of steel 30Cr2Ni4MoV at different locations of an LP steam turbine rotor were researched by chemical composition and microstructure analysis, room- and high-temperature tensile tests, room-temperature impact and hardness tests, as well as fracture appearance transition temperature (FATT) tests, so as to study the variation mechanism of its mechanical properties and structure. Results show that at different locations of rotor, the segregation of chemical composition is relatively small, the change of grain size is not obvious, the tensile strength and hardness are very uniform, but the room-temperature impact values, the energy of fracture transition plastic and the FATT are quite different. Both the room-temperature impact value and the energy of fracture transition plastic on rotor surface are higher than at rotor core, however, the FATT on rotor surface is lower than at rotor core.