The invention relates to a method for adjusting and controlling a melt separation titanium slag crystallization phase. According to the method, the components of titanium slag are adjusted and controlled to comprise, by weight, 40-70% of TiO2, 4-18% of MgO, 4-18% of Al2O3 and a reducer, wherein the weight ratio of the reducer to TiO2 is 0.01-0.15; and the titanium slag is heated to be melted, after complete reacting, the temperature is decreased to be 1300-1500 DEG C at the speed rate of 0.1-20 DEG C / min for quenching treatment so as to obtain the melt separation titanium slag. According to the method for adjusting and controlling the melt separation titanium slag crystallization phase, through adjusting and controlling over the components and controlling over the crystallization process,anosovite becomes a sole precipitated phase of the melt separation titanium slag, the TiO2 grade of an anosovite titanium-rich phase in the melt separation titanium slag is high, the grain size is large, the mineral phase structure is compact, the single separation degree is high, and after subsequent treatment, the high-grade titanium slag with the TiO2 grade being 76% or above can be obtained. According to the method for adjusting and controlling the melt separation titanium slag crystallization phase, the requirement of a sulfate process titanium dioxide technique for the titanium slag grade is met, and the method is suitable for industrialized application.