The Mo-Si alloy sheets with different silicon contents were fabricated by powder-metallurgical processing, and static tensile tests were performed at 25, 300, 800 and 1200 ℃, respectively. The effect of test temperatures on mechanical properties, facture mode and microstructure of Mo-Si alloys were studied. The results indicate that with increasing of tensile test temperature, the strength of the pure Mo and Mo-Si alloy sheets decrease dramatically, the elongation shows an increasing trend at lower 300 ℃ and then decreasing at higher temperatures. The fracture mode of molybdenum alloy sheets transform from transgranular cleavage fracture at room temperature to dimple fracture at 300 and 800 ℃, and then to intergranular fracture at 1200 ℃. The strengthening mechanism analysis results show that the strengthening of Mo-Si alloy originates from particle dispersion strengthening and solid solution strengthening at room temperature. While, at elevated temperature the role of solid solution strengthening weakens significantly and the particle dispersion strengthening and grain coarsening are main strengthening modes