The Mo5Si3 base alloys with a series of transition metal elements were prepared by arc-melting, and were annealed at 1250°C in vacuum for 24 h. Ternary alloying effect was investigated by X-ray diffractometry (XRD), optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The EDS results show that Zr, Ti, Co and V have certain solubility in homogenized Mo5Si3, which are determined to be 2.20±1.42, 15.94±0.18, 3.33±0.76 and 7.43±0.22 (mole fraction, %), respectively. Microstructural characteristics indicate that all studied alloys have a two-phase microstructure, i.e., Mo5Si3 matrix and the second phase Mo37Zr20Si43, Mo66Si19Ti15, MoCoSi or (Mo, V)3 Si.