A new method is proposed for machinability evaluation of machinable ceramic materials. The relation of machinability attributes is modeled as a digraph, and machinability attribute matrix is defined. Machinability indexes are calculated with permanent function of the matrix, and machinabilities of machinable ceramics are ranked. Five composites consisting of CePO4 and zirconia were fabricated, measured and drilled with tungsten-cobalt carbide bits. Mechanical property parameters of Ce-ZrO2/CePO4 composites, including Vickers hardness, fracture toughness and Elastic modulus, are selected as machinability attributes. The experimental results of material removal rates are consistent with the ranking of machinability index values of Ce-ZrO2/CePO4 ceramics. The machinabilities of Ce-ZrO2/CePO4 ceramics improve with the increase of CePO4 proportions. Machinability of machinable ceramics can be evaluated with digraph method.