The invention provides a method for preparing polyethylene from a rare earth compound, and belongs to the field of macromolecular material synthesis. The method comprises the following steps of putting a water-free and oxygen-free reaction kettle into a glove box; maintaining an inert gas atmosphere; adding a methylbenzene solution; performing stirring; heating the materials to 25 to 50 DEG C; introducing ethylene gas; performing heat insulation for 5 to 10min; mixing organic borate and alkyl aluminum; using toluene for dissolution; adding the materials into the reaction kettle; after 2 to 5min, adding the rare earth compound dissolved by the toluene into the reaction kettle; starting the polymerization, wherein the polymerization time is 30 to 240min; after the polymerization is completed, relieving the pressure of the reaction kettle; adding a great amount of methanol for cleaning; putting the obtained polymer precipitates into a vacuum drying box to be dried; obtaining polyethylene. The method has the advantages that the rare earth compound is used as a catalyst, the polyethylene polymerization is realized; the consumption of the rare earth compound is low; the activity is high. The melting point of the prepared rare earth polyethylene is high; an extension chain structure is realized.