Under condition of practical turning constraints,a bi objective multi pass turning optimization model,based on surface roughness and energy consumption,was very necessary for the optimization of machining parameters.The Non dominated Sorting Genetic Algorithm-II (NSGA-II) and the Multi-objective Particle Swarm Optimization (MOPSO) were applied to the multi-pass turning optimization model.Example of optimization shows that the Pareto-optimal solutions set for surface roughness and energy consumption,and the corresponding machining parameters both precise and rough obtained by the NSGA-II Algorithm are more excellent than example results of MOPSO,which provides practical guides for selection optimization of machining parameters in multi-pass NC turning.