Laser Raman microprobe (LRM) is a reliable technique for phase identification to analyze the molecular composition and microstructure on 1 μm2 area of samples, and therefore, it is well-suited for identifying the mineral phases of single fine particles. In the present paper, we utilized LRM to identify the mineral phases of the single inhalable particles (PM10) from samples in Beijing City and compared the Raman microscopic spectra of samples with the standard spectra of mineral and inorganic material of Renishaw’s database. Then we confirmed, for the first time, that the mineral phase of Ti-rich particles in the environmental atmosphere is the anatase TiO2, whose Raman spectrum has a strong O—Ti—O band at 638 cm-1 and two medium O—Ti—O bands at 398 and 517 cm-1 respectively. Thus it ensures the existence of TiO2 particles in PM10. Anatase is an important photocatalyst which can speed up the heterogeneous reaction between mineral particles, especially the calcium carbonates, when carried by these particles. Furthermore, the crystal structure of anatase, relative humidity of environment and the surface pH value can significantly influence the photocatalysis of anatase in atmosphere.