Anodic titanium dioxide (ATO) has been investigated for decades of years. It can be widely used in microextraction fiber for sample pretreatment because of its rich variety of morphologies such as nanotube, nanowires, nanoparticles and so on. In this work, TiO2 nanotube clusters in situ growth were prepared on titanium substrate by anodization method. The effects of anodization distance, anodizing time and temperature of electrolyte were investigated. The results showed that uniform nanotube clusters coating can be obtained under the conditions of 1.5 cm anodizing distance, 50 min anodizing time and 60 °C anodizing temperature. On this basis, a novel, simple and fast octadecyl functionalization was followed by one step chemical self-assembly method based on the chemical reaction between octadecyltrichlorosilane and surface titanium hydroxyl groups (Ti-OH). The electrochemical scanning microscope (SEM), energy dispersive spectrometer (EDS) and XPS were employed for sample characterization, which showed that octadecyl groups were successfully assembled on the surface of TiO2 nanotube clusters. Moreover, the surface corrosion resistance of the fibers was also tested by electrochemical methods.