The microstructures and mechanical properties of arc-melting processed Mo3Si-Mo5Si3 eutectic have been investigated. The Vickers hardness of Mo3Si-Mo5Si3 eutectic alloy at room temperature is on the order of 1350Hv. The fracture toughness value of the alloy at room temperature is 1.39MPam(1/2) measured by Single edge-notched beam specimen technique and 1.61MPam(1/2) measured by Indentation technique. The compressive strengths at 1300degreesC and 1400degreesC under a strain rate of 10(-4)S(-1) are about 550MPa and 300MPa respectively.