Abstract: Using explosive-driven flyer to compact mixture powders of TiO<sub<2</sub< and copper, two different TiO<sub<2</sub< particle size (60 nm and 1.5 <i<μ</i<m) used to investigate the size effect on shock-induced phase transition. XRD, Raman and SEM tests for retrieved powders all confirm Rutile-to-Srilankite phase transition with both sizes, micro-scale TiO<sub<2</sub< high pressure phase transition rate reaches 93%, far higher than the nano-scale phase transition rate, which is only 45%. SEM shows that these shock-treated powders are ellipses within the size range of 0.5~2.0 <i<μ</i<m. This result shows that bigger particle size of TiO<sub<2</sub< will facilitate the exposure and detainment of high pressure phase during the shock-induced phase transition of TiO<sub<2</sub<.