A new method was developed to synthesize high active TiO2 nanocrystals by the hydrolysis of titanium (IV) chloride in water at 40-80°C, employing nanocrystal cellulose (NCC) as morphology controlling agent. The obtained samples were characterized with transmission electron microscopy (TEM), X-ray diffraction (XRD), and ultraviolet-visible spectrophotometer. TEM investigations revealed that the crystals synthesized at 40-60°C were flower-like which was composed of nanoneedles, and when the temperature rose up to 70-80°C, cubic nanocrystals with an edge length of 100-200 nm were observed. XRD results showed that the crystalline phase of the nanocrystals had a strong dependence on the temperature and aging time, and the content of rutile phase increased with increasing either the temperature or the aging time. The photocatalytic activities of the samples were tested by the degradation of methyl orange in aqueous solution under high pressure mercury lamp. The experimental results revealed that cubic nanocrystals showed much higher photoactivity than flower-like ones.