A novel continuous process has been developed, which consists of a two-stage slug flow tubular reactor (SFTR) to increase the size of titanium dioxide fine particles. In a single-stage process, particle growth stops at a certain conversion level with unreacted titanium ethoxide remaining. In this process, however; water is added to the particle suspension containing unreacted titanium ethoxide to allow the particle growth to proceed again. The particles prepared using the two-stage SFTR process have a larger mean particle size and smaller geometric standard deviation (GSD) than those from the single-stage process. The two-stage process also provides a higher conversion to particles than the single-stage process does. A smaller amount of water fed into the first stage and a larger amount of water fed into the second stage results in a larger mean particle size, higher conversion to particles, and smaller GSD. The width of the particle size distribution of the two-stage process is almost the same as that of the single-stage process. The calculated results using a mathematical model are in agreement with the experimental data.