采用第一性原理计算了金属间化合物α-Nb5Si3,β-Nb5Si3和γ-Nb5Si3的结构稳定性、弹性常数、热力学性质和电子结构,并利用Voigt-Reuss-Hill方法计算了弹性常数。结构参数优化结果与实验值基本一致;结合能和形成焓结果表明α-Nb5Si3的结构稳定性最好。最后分析和讨论了3种不同Nb5Si3相的延展性和弹性各向异性。 The structural stability, elastic constants, thermodynamic properties and electronic structure of the intermetallic compounds α-Nb5Si3, β-Nb5Si3 and γ-Nb5Si3 were calculated by the first-principles principle. The elastic constants were calculated by Voigt-Reuss-Hill method. The results of the optimization of structural parameters are basically consistent with the experimental ones. The results of the binding energies and the formation enthalpies show that the structural stability of α-Nb5Si3 is the best. Finally, the ductility and elastic anisotropy of three different Nb5Si3 phases were analyzed and discussed.