The impurity concentrations of Fe, Ni and Cr in Ti sponge determine its quality and application areas. In order to analysis the inflow process of Fe, Ni and Cr impurities in Ti sponge during Kroll process, the concentration distributions and enrich phases of impurities were investigated by testing the samples that taken from different parts of the Ti sponge mass, and the mixing enthalpies of Ti?Mg?Fe, Ti?Mg?Ni and Ti?Mg?Cr were calculated by Miedema model. The results indicated that the Fe, Ni and Cr impurities from the reactor which manufacture material was stainless steel (1Cr18Ni9Ti), and the inflow process could be divided into two step while TiCl4 was feeding: Fe, Ni and Cr atoms dissoluted in liquid Mg, alloying with Ti sponge for strong atomic force between Ti?Fe, Ti?Ni and Ti?Cr atoms. In order to obtain high quality Ti sponge which has lower impurities contents of Fe, Ni and Cr, following steps should be taken: coating the reactor inner surface with a titanium film, controlling the reaction temperature strictly, using lower Fe, Ni and Cr content liquid magnesium as raw material, separating the edge and bottom part of the Ti sponge mass.