The invention discloses a locking plate disassembling tool and method of a turbine rotor assembly. The disassembling tool comprises a positioning device used for centering and fixing a turbine disk soas to prevent the turbine rotor assembly from rotating, a supporting device arranged on a tenon of a blade in a removable mode and between the free end of a locking plate and the edge of the blade, and a prying device used for prying the free end of the locking plate with a supporting face as the support point so as to separate the locking plate from the surface of the tenon, wherein the side, facing the free end of the locking plate, of the supporting device is provided with the supporting face. The supporting device is arranged between the free end of the locking plate and the edge of the blade and on the tenon of the blade, the supporting face on the side, facing the free end of the locking plate, of the supporting device provides the support point for the prying device, the prying device adopted for prying the free end of the locking plate with the supporting face as the support point so as to separate the locking plate from the surface of the tenon, the locking plate has the support point when the prying device pries the locking plate, and therefore slip is not likely to occur when the locking plate is pried, and the turbine disk or the tenon of the blade is prevented from being damaged after being hit or being scratched.