The relative machinability of the invar-type cast alloys, such as invar cast steel, invar-type cast iron, Meehanite cast iron, and the modified Invar-type cast iron containing Mo and V was evaluated based on the tool life test, the surface roughness test and the chipping test. Tool life and surface roughness were measured under various rotting conditions. The tool lives of Invar cast steel, Meehanite cast iron, the modified Invar cast iron and Invar cast iron was 12min, 8min, 1min, 41min, respectively. The surface finish of Invar cast steel and the modified Invar cast iron was better than that of Meehanite cast iron, and the chip breakability of invar cast iron and Meehanite cast iron was better than that of invar cast steel. The Taylor`s equations of invar cast steel and the modified invar cast iron were VT＾(0.3076)=154.479 and VT＾(0.3880)=102.326, respectively. As the cutting speed increases, the surface finish of the modified invar cast iron was improved.