Rutile TiO₂ nanoparticles were synthesized by self-hydrolysis of TiOCl₂. Rutile phase was detected by XRD at 50°C. As the reacting temperature became higher, the XRD peaks of anatase appeared and the peak intensity of both phases became larger. The roundish agglomerates surrounded by acicular particles were observed by SEM at 50°C and acicular particles grew with elevating temperature. These results indicate that the crystal growth of rutile was promoted at high temperatures. When the pH value of starting solution became lower by addition of HCl, only rutile phase was detected by XRD even at high temperatures. This is because the deprotonation was suppressed under low pH value, leading to predominant formation of rutile. In this study, we obtained small acicular particles of rutile crystalline by addition of HNO₃.