This paper chose multi-index to provide a comprehensive evaluation model to evaluate the use reliability of CNC machine tools as a single assessment indicator is biased. As the number of evaluation factors is huge and it is difficult to get the exact values, a fuzzy theory is applied. Reliability mathematical model and maintainability mathematical model were established based on failure data selected from filed test and calculated the estimation values of reliability indexes. Subsequently, a fuzzy comprehensive evaluation mathematical model of CNC machine tools was constructed which combined fuzzy with comprehensive evaluation theory. Using this model could evaluate reliability level of CNC machine tools accurately and integrative.