An environmentally benign route has been developed to synthesize monodispersive anatase TiO2 nanocrystals in organic solvent. The water-soluble peroxotitanium acid (PTA) was used as the precursor, which made the reaction practicable and facile in the microfluidic reactor. The perfectly crystallized anatase TiO2 nanocrystals with a mean diameter of about 5.0 nm were obtained via a microfluidic reactor with a time as short as one or two minutes.