With the kinetic Monte Carlo simulation of smooth (001) surface of symmetry-broken simple cubic crystal in fluid with low supersatuaration rate, the mechanism of nanowire growth based on crystal nuclei on the surface is discovered and the morphology of nanowire is obtained. The dependences of nanowire morphology on thermal roughness in the longitudinal and latitudinal direction and growth time on the anisotropic surface of the crystal are further discussed. The relations of nanowire growth rate with thermal roughness, supersaturation rate, surface size and diffusion rate on the surface are then systematically studied.