A crosslinkable polysiloxane molecule is in the form of a polysiloxane polymeric chain with a pendant group, that is, a benzoxazine group, and thus is capable of undergoing a cross-linking reaction spontaneously to produce a crosslinkable polysiloxane polymeric material. The benzoxazine group enhances the compatibility between a polysiloxane polymer and a conventional organic polymeric material, functions as a polymer flame retardant or reaction-oriented additive, and widens the application of a polysiloxane polymer to organic polymeric materials in property adjustment and the applicability of the organic polymeric materials.