The quality of CNC (computer numerical control) machine tool is the key to the survival of manufacturing enterprises. How to comprehensively and accurately evaluate and analyze its quality is very important for the timely discovery and improvement of machine tool defects. The current research either only evaluates and analyzes a certain quality characteristic of CNC machine tool, or ignores the dynamic nature of CNC machine tool quality parameters, which reduces the accuracy of quality analysis results. To address this problem, firstly, reliability, maintainability and supportability were taken as the comprehensive evaluation indexes of CNC machine tool quality characteristics, so as to improve the comprehensiveness of the analysis. Secondly, on the basis of considering the dynamic characteristics of machine tool reliability, the ADC (availability, dependability, capability) model was improved to obtain a comprehensive quality evaluation index function E RMS with time-varying characteristics. Finally, the characteristics of E RMS were analyzed, and its specific evaluation criteria were also given. Several CNC machine tools were tracked, and the method proposed in this paper was applied. The E RMS of the machine tools was obtained, and its characteristics were analyzed. The results verify the correctness of the proposed method, and provide theoretical basis and technical support for the improvement of the quality of CNC machine tool and the market competitiveness of manufacturing enterprises.