With a Tersoff-potential based MD(molecular dynamics) method, thermal-stability and tensile properties of Si_o-H(hydrogenated outside) and Si_io-H(hydrogenated outside and inside) single wall nanotubes are investigated. Compared with a(14,14) carbon nanotube, the axial-tensile properties of Si_o-H and Si_io-H nanotubes are discussed. The results show:1)The Si_o-H and Si_io-H nanotubes have similar Si skelectons with t {110} crystal-pane of a single-crystal silicon and exist stably only at a temperature lower than 150 K and 75 K, respectively. 2) Si_o-H and Si_io-H nanotubes have anti-tensile strength of 4.0 and 1.2 GPa, and fracture strain of 35% and 32%, respectively, which are much lower than those of a(14,14) carbon nanotube.