A new preparation method of particles was introduced, which consisted of a continuous aging tube to decrease the size of TiO2 fine particles. The particles prepared by using a continuous aging tube method had a smaller mean particle size and smaller standard deviation than those obtained from the batch or semibatch process. In this work, it was found that the size of TiO2 particles decreased with increasing reaction temperature and residence time in the aging tube. However, the particle size increased with increasing the diameter of aging tube. By using the above conditions, mean diameters as small as 30 nm were obtained.