The invention provides novel abietane type diterpene compound. According to a preparation method of the abietane type dieterpene compound, dried clerodendrum longilimbum branch fragments are utilized as a raw material, the raw material is heated and reflux extracted by alcohol solution, and an extracting solution is repeatedly treated by silica column chromatography, reversed-phase C18 column chromatography, gel column chromatographic separation to obtain monomer compound of 12(16),8(9)-diepoxy-18(4-3)-shifttransfer-3,5,12-abietane triene-7,11,14-triketone which is shown by a formula (I) shown in the description. The obtained novel compound disclosed by the invention has very good antitumor activity, provides novel compound or lead compound with medical value for medical industry, has simple operation in a preparation process, achieves large-scale production and improves medical value of clerodendrum longilimbum.