In the field of industrial manufacturing,hydraulic system is an important unit in CNC machining.Because of its quantitative and qualitative characteristics in the reliability distribution and is affected by multiple factors and multiple levels,the improved fuzzy analytic hierarchy process (FAHP) was adopted,the six factors affecting the hydraulic system were determined through comprehensive consideration,the three-scale evaluation rules were established,the fuzzy consistency matrix was determined,and a fuzzy hierarchical structure model was built.Program for the improved FAHP model was written in MATLAB environment,expert data were imported,the comprehensive weight of each object layer unit to the target layer was calculated and determined,and the reliability of the hydraulic system was assigned according to the determined weight.It provides new ideas for the design of hydraulic system for CNC machine tools and reliability research.