This invention relates to a method of preparing envelope powder. The shattering, depolymerization and coating processed at same time, and solid phase acid-base reaction participate the method. This envelope powder possess double-decker or three-layer structure, inner core is composed by oxide or hydrate or inorganic oxysalt, crust composed by inorganic oxysalt, envelope by aluminum phosphate or boron phosphate. This low cost powder be able to used as fortifier, power stuff, colorant and so on, applied to plastic, rubber, ceramics, dope, binder and paper, set foundation for popularization of ultramicro and nanometer powder.