The numerical control machine tool, which is a typical energy-using product, because there are all sorts of energy loss and auxiliary functions, has low efficiency in machining process. Author makes a study of NC machine tool energy consumption controlling. With simens840Dsl numerical control system as an example, based on the analysis of CNC system control principle, according to processing characteristic of the part, the macro program is wrote to optimize dynamic characteristics of NC machine tool. According to the machine idle time in different work condition, three energy-saving control profiles are formulated, including machine standby, NC standby, auto shut off. By the formulation of the corresponding PLC control logic, low energy consumption of intelligent control of NC machine tool is realized. Integrate PAC3200/4200 multi-function meter in NC machine tools, quantitative measurement and analysis of energy consumption for numerical control system and ancillary equipment can be implemented, and machine tool real-time energy data can be obtained. This scheme has been successfully applied in long-men portable CNC machine tools, and obtained the ideal effect: to realize the optimize control of energy consumption, improve the performance of the machine tool, become more market competitiveness.