Quantitative XRD measurements of the nanosized TiO2 particles obtained from the detonation soot have been carried out. The lattice parameters, such as grain size, cell volume, lattice constants and lattice strain were obtained. The relationships between the change ratio of cell volume (the reciprocal of the particles size, or the mass ratio of explosive and TiO2 precursor) and the lattice strain of the different TiO2 phases were also discussed. The relationship between the change ratio of cell volume and the particle size of TiO2 particles was also studied. The results demonstrated that with the decreasing of the particles size, the lattice strain of anatase phase increased, while the lattice strain of rutile phase increased firstly and then decreased to some extent. It is different from the linear relationship between the lattice distortion and the reciprocal of the particles size reported in other literatures. In the meantime, the lattice strains were different with the different mass contents of RDX in the microstructures of the TiO2 particles. The direct reflection of microstructure changes is the changes of the particle size of TiO2 particles. Based on the XRD results, the particular characteristics of the detonation process and interfacial effects of nanocrystalline materials, a crude explanation was also given.