As the basis of mechanical manufacturing, machine tool geometric error, thermal error and assembly error will all affect the machining accuracy of numercial control (NC) machine tool. The machining accuracy of NC machine tool directly decides the production quality of products. In order to ensure the processing quality of NC machine tools for product, the data of machining error of NC machine tool is processed in need to obtain the reliability of NC machine tools machining precision. As a second moment method and Monte Carlo method are common methods of reliability analysis, the reliability of NC machine tools machining precision was analyzed by using the above two methods aimed on the given error data about the three axis NC machine tool as a research object. This analysis is of important guiding significance and reference value for improving machining accuracy of NC machine tools and ensuring service life.