Increasing pressures from a variety of directives and standards have caused the manufacturing enterprises to consider and initiate implementation of energy assessment and energy quota practices to improve both their economic and environmental performance. Therefore, in view of the complexity of machining system's energy consumption and the difficulty of data collection for energy analysis, a simplified and practical energy consumption model for machining system based on Coloured Petri Net (CPN) was proposed. Firstly, the energy flow of machining system was analysed. And then the energy consumption model of the machining system processing various tasks based on CPN was proposed, where the calculation method of energy use during production was simplified and it was determined by four parameters: idle power of machine, machining time, material pattern, and material removal volume. Finally, through the case study of a machining system with two tasks, the proposed energy model was simulated and the simulation results were proved to be significant in practice.