The molybdenum alloys doped with various mass fraction zirconium diboride (ZrB2) particles were successfully prepared by using the powder metallurgy technology. The microstructure, hardness and the tensile properties of the pure molybdenum and molybdenum alloys doped with ZrB2 particles were determined at room temperature. Results showed that the addition of zirconium diboride refined the molybdenum grains obviously, meanwhile, molybdenum grain sizes decrease with the increasing of zirconium diboride mass fraction. Measurements on mechanical properties showed that molybdenum alloys doped with ZrB2 particles had higher hardness and strength than pure molybdenum. The analysis and discussion results show that the strengthening mechanisms of ZrB2-doped molybdenum alloys may be attributed to the fine-grain strengthening, particle dispersion strengthening, interfacial-bond strengthening and oxygen reduction strengthening.