In this paper, the formation of titania nanotube arrays was investigated in NH4F/H2SO4 electrolyte. Under optimized electrolyte conditions, the titania nanotube arrays with an inner diameter of about 120 nm and a length of about 300 nm was obtained. During the formation process. the variety of current was observed. The current-time curve implied that the evolvement process of titania nanotube arrays include three stages. The stability of titania nanotube arrays at elevated temperatures was studied. The as-prepared titania nanotube arrays is amorphous. crystallized in anatase and rutile as the rising of the temperature. The samples were characterized by ESEM and XRD.