The influence of mechanical activation time on mechanochemical behavior of the CaHPO 4 -Ca(OH) 2 -CaF 2 -TiO 2 system was investigated. Results showed that a fluorapatite-titania (FAp-TiO 2 ) composite nanopowder with high phase purity was obtained after 15 h of milling. Detailed study of microstructure by transmission electron microscopy confirmed the formation of the cluster-like composite nanopowders. This structure was composed of ellipsoidal nanoparticles with an average diameter of 16 ± 7 nm after 15 h of milling. Unit cell measurements indicated that the a-axis and caxis values of FAp in the composite structures were similar to the reported values for the standard. After 5 h of milling, the crystallite size and lattice strain were about 23.11 nm and 0.64 %, respectively. With increasing the milling time to 15 h, the lattice strain increased to about 0.70 %, while the crystalline size declined to around 21.66 nm. Based on the obtained data, the fraction of crystalline phase (crystallinity degree) was strongly influenced by the milling time. Accordingly, the crystallinity degree of the composite nanopowder reached a maximum about 38.32 % after 15 h of milling. According to the FT-IR and EDX results, the 15 h milled sample had high chemical purity.