The invention belongs to the technical field of copper-clad plate production and particularly relates to a preparation method of a halogen-free high Tg copper-clad plate. According to the invention, a polyfunctional group phosphorus epoxy resin is used as a matrix resin in combination with a phenol novolac epoxy used to improve the heat resistance of the plate and increase the glass-transition temperature of the plate, aluminum hydroxide used to improve the flame retardance of the plate, and talcum powder used to further improve the heat resistance of the plate. Surface treatment and particle size control are carried out to the aluminum hydroxide and talcum powder fillers, and the various materials are stirred and mixed by means of a high shear kettle disperser and an emulsifying motor, such that the fillers are uniformly dispersed into resin glue and glass fabric to improve the toughness of the plate. The total halogen content is less than 900 ppm, thus meeting the halogen-free requirement of European Union and the like. The produced copper-clad copper has high glass-transition temperature with a Tg value of greater than 160 DEG C in addition to basic properties such as electrical properties and insulation property of a conventional halogen-free copper-clad plate.