This research investigated the growth characteristics of TiO₂ nanoparticles in the instantaneous high-temperature and high-pressure gaseous detonation reaction. Computational fluid dynamics was used to simulate the flame propagation process and the temperature-time relationship of the gas explosion in the detonation tube, and it was introduced into the particle growth model. The model was modified through experiments. The results show that the reaction temperature and time are the main factors affecting the particle growth in the gaseous detonation reaction. A particle size correction coefficient k is proposed to improve the classical particle growth model. The improved numerical model can accurately predict the growth characteristics of TiO₂ nanoparticles, which provides effective theoretical support for the controllable synthesis of TiO₂ nanoparticles.