Data envelopment analysis (DEA) evaluation system of metal materials was established. Evaluated metal materials were regarded as decision making units (DMUs). Property parameters of metal materials were selected as inputs of DMUs, and machining process parameters were selected as outputs of DMUs. Input and output data sequences could be obtained through data processing operations. Mathematics programming model was founded and optimal values of all the evaluated materials were calculated based on the model. Machinabilities of metal materials could be evaluated by comparing the optimal values. Taken 1Cr18Ni9Ti, GCr15, Q235, 45# and LY11 for example, machinabilities of five metal materials were ranked. Research results suggest that DEA method can synthetically consider the relationship between property parameters and machining process parameters. DEA is proved to be a reasonable and available method to evaluate metal material machinability.