Abstract: The effect of wollastonite on crystallization properties and crystallization phase of mould powder made of cement clinker and industrial mineral raw materials in laboratory had been studied through process mineralogy. The results show that the crystallization temperature decreases with the content of wollastonite increasing at the same cooling speed. The critical cooling rate decreases by 2 ℃/s when increasing 2% wollastonite. And increasing wollastonite content leads to long incubation time of crystallization which can improve the lubrication degree of slab. When the content of wollastonite ranges from 11% to 19%,the crystallization ratio of the resulted mould flux is more than 80% where the main minerals in flux film are cuspidine and wollastonite. The contents of the two kinds of crystallization phase are similar when wollastonite is less than 15%. However,when the content of wollastonite is above 17%,the crystallization phase consists of more wollastonite and less cuspidine. At the same time,the viscosity increase somewhat but the heat flux increase obviously which is unbeneficial to control heat transfer. To achieve the balance of heat transfer and lubrication,the suggested content of wollastonite is 15% or less.