This invention discloses a method for synthesizing a new ent-kaurene diterpenoid compound and its derivatives. The chemical structure of the ent-kaurene diterpenoid compound is shown in this invention. The method comprises: soaking the aerial part of Rabdosia rubenscens in organic solvent at 40-60 deg.C for 3 h-3 days, concentrating to remove the majority of solvent, and separating the concentrateby macroporous adsorption resin and silica gel repeatedly to obtain oridonin A. The ent-kaurene diterpenoid compound can be used as an ideal intermediate for asymmetric organic compounds and drugs, and can be also used as anti-tumor, anti-inflammatory and immuno drugs. The ent-kaurene diterpenoid compound can condense with hydroxyl compounds to obtain various acetal derivatives, can react with amino compounds to obtain various amino derivatives, and can react with acyl halides and carboxylic anhydrides to obtain various acyl derivatives.