Reliability allocation is a collection problem of engineering decision, multiple factors comprehensive balance and process optimization. Considering that both the factors that influenced the reliability allocation and their weights have the characteristics of uncertainty, which always be ignored .Therefore a subjective and objective combined weights method that combined the entropy method and Interval analysis method was proposed. Taking NC grinding machine as an example, firstly, establish the reliability objective function based on the minimum discrimination information principle, and employ the Lagrange multiplier to get the combined weights of the 6 factors. Then use the fuzzy comprehensive allocation method to obtain the reliability allocation results, which was compared with the actual accumulated data, so that the feasibility and effectiveness of this method was verified.