Magnetic properties of magnetic transition metals doped in the infinite Si nanotubes (SiNTs) with hexagonal prism structure ([Si.sub.12] [M.sub.n], M = Fe, Co, Ni, n, = 1,2) have been investigated for two different numbers of dopants per hexagonal prism by using the localized basis calculational method. The decrease (increase) of spin-down (spin-up) electrons for the n = 2 case results in the increase of magnetic moments compared with the n = 1 case. The calculated magnetic moment per dopant Fe atom (2.39 [[micro].sub.B]) is larger than both of the bulk value (2.22 [[micro].sub.B]) and previous result for finite nanotube (1.7 [[micro].sub.B]). For Co and Ni atoms doped in the tube, the magnetic moments are smaller than those of bulk metals. The Si-Si bond lengths for the hexagonal prisms decrease compared with that of the nanotube without transition metals, but there is no dependency on different dopants. The distances between the transition metals and Si atoms decrease as the atomic number of transition metals increases, which is the same trend for the atomic radii of transition metal atoms. The doping of transition metal atoms leads to the increase of the binding energy (BE). Index Terms--Binding energy, hexagonal prism structure, magnetic moment, silicon nanotube, transition metal encapsulation.