Three kinds of single metal oxide (MnO2, ZnO, and AlO(OH)) and one complex metal oxide (K2O·6TiO2) having nano structure of wire, rod and ribbon were rapidly synthesized by hydrothermal synthesis in supercritical water. Aqueous Mn(NO3)2, Zn(NO)2, Al(NO3)3 solutions and mixtures of TiO2 sols and KOH solutions were used as starting materials, respectively. Syntheses of these nanostructured materials were performed by a flow type apparatus. We investigated the relationship between reaction parameters (temperature, pH and reaction time) and morphologies of the products. Reaction temperatures were 350, 400, and 420 °C. Reaction time is in the range of 1.8 – 116 s. The product was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that particle morphologies strongly depend on pH for MnO2 and ZnO. MnO2 nanowires with 10 nm in diameter and ZnO nanorods with 50 nm in diameter were obtained from acidic metal salt solutions. In the case of AlO(OH), temperature and time were key parameters for crystal growth. In the case of K2O6TiO2, larger fibrous particles with 50 nm in diameter were obtained at higher reaction temperature.