A reliability analysis framework is constructed by combining parametric modelling methods with finite element analysis methods under fluid-thermal-solid sequential coupling. The influence of blade profile changes due to machining errors on the reliability of turbine rotor blisks in reusable rocket engines (RRE) is investigated. The effects of machining errors, material, and load variability on the cyclic life reliability of rotor blisks are effectively quantified. With the suggested method, a reliability analysis is conducted for an RRE turbine rotor blisk, and the effect of the machining error range on the analysis results is investigated. It is found that when the reliability requirements are 0.85, 0.9, and 0.95, the general tolerance grades to satisfy the reliability requirements are the coarsest grade, the medium grade, and the precise grade, respectively. The highest sensitivity coefficient in cyclic life reliability is 29.09% for the blade axial chord. This study provides valuable insights and recommendations for the reliability design and optimization of reusable turbine rotor blisks.