Ti foil was put into the NaOH solution and TiO2 nanowire array films were prepared by a hydrothermal method. The effects of hydrothermal parameters on the nano-structured TiO2 and its growth mechanism were systematically studied. The samples were characterized by FESEM, XRD and TEM. The results show that the dynamic equilibrium between the dissolution of Ti and crystal growth of titanate is the main influencing factor for structures and morphologies of the products. At the same temperature, the decreased concentration of the NaOH solution leads to the increased dimension of the hydrothermal products. The temperature rise can accelerate the dissolution of Ti and the diffusion of titanate, and the products grow along linear dimension. Meantime the high temperature makes more complete crystal structure. The prepared TiO2 nanowire array exhibits good optical and electrical properties.