Spherical Nb-Si powder alloy is a perspective material to manufacture products for the aerospace industry by additive technologies. Nb-16Si (at.%) powder alloy was prepared by mechanical alloying from pure elemental powders using planetary ball mill Fritsch Pulverisette 4. Spheroidization was carried out on plasma generator based on thermal plasma arc generator with vortex discharge stabilization. Experimental results show that plasma spheroidizing of Nb-16Si powders obtained by mechanical alloying is possible. It is shown that after the spheroidization the particle surface is rough which indicates the cast structure of the material. Three phases having different optical contrast are revealed on microsections: Nb5Si3, Nb3Si and Nbss, which is confirmed by X-ray diffraction. It is shown that the main peaks in the X-ray graph after MA correspond to a solid solution of niobium with a cubic lattice and the parameter a = 0.333 nm, as well as niobium silicide Nb5Si3 with a hexagonal lattice (P63/m) a = 0.7536 nm and c = 0.5249 nm. After spheroidization the hexagonal lattice of niobium silicide Nb5Si3 is transformed into a tetragonal lattice (I4/m) with the parameter a = 0.6557 nm and c = 1.186 nm. The other phase components remain unchanged.