Error compensation is an effective method to improve the accuracy of NC machine tool.The compensation results are greatly affected by the error modeling and error measurement,so how to establish an accurate error model and accurately detect the geometric errors of machine tool are particularly important.In the paper,the volumetric error model of a multi-axis NC machine tool is established based on the multi-body system theory.The relative position deviations between the rotary axis and linear axis of the machine tool are considered in the modeling.To achieve quick and accurate detection,a laser tracker is based on the multi-station and time-sharing measurement principle to detect the geometric errors of machine tool,and each error of linear axis and rotary axis can be identified by this method.With the error model,error compensation can be carried out by modifying the machining process(G code),and the machining accuracy can be improved with the new G code.Experiment results show that the motion errors of a milling machine are significantly reduced after compensation,which verifies the effectiveness of compensation method. Error compensation is an effective method to improve the accuracy of NC machine tool. The compensation results are greatly affected by the error modeling and error measurement, so how to establish an accurate error model and precisely detect the geometric errors of machine tool are particularly important. In the paper, the volumetric error model of a multi-axis NC machine tool is established based on the multi-body system theory. The relative position deviations between the rotary axis and the linear axis of the machine tool are considered in the modeling.To achieve quick and accurate detection, a laser tracker is based on the multi-station and time-sharing measurement principle to detect the geometric errors of machine tool, and each error of linear axis and rotary axis can be identified by this method .With the error model , error compensation can be carried out by modifying the machining process (G code), and the machining accuracy can be improved with the new G code. Experiment results show that t he motion errors of a milling machine are significantly reduced after compensation, which verifies the effectiveness of compensation method.