Abstract: A method for the determination of the conversion rate of rutile seed in the production process of titanium dioxide is introduced. The phase composition of rutile seed, i. e., Rutile(R), Anatase(A) and NaCl was analyzed by the X-ray diffraction(XRD) method. In the sample pretreatment, by controlling pH of the system near the isoelectric point of rutile seed and centrifugal desalination, the overlapping interference of the diffraction peaks of NaCl (111) on the surface of rutile (110) was eliminated, and the volume fraction of low content titanium anatase was increased. The rutile conversion rate of crystal seeds was determined quantitatively by the "adiabatic method".