The invention provides modified talcum powder and a preparation method thereof. According to the technical scheme provided by the invention, a brucite component in the talcum powder can react with a pretreatment agent, so that Vander Wale force of the talcum powder is damaged; interlayer stripping is generated; meanwhile, the size of the talcum powder is decreased; through treatment of a coupling agent, the agglomeration of the talcum powder can be effectively avoided. Through the modified talcum powder obtained by the modification method, the phenomenon of agglomeration of the talcum powder can be avoided.