Based on investigation of the thermogravimetric curve TG/DTG of dehydroabietic acid diethylenetriamine salt (II), a method for preparation of dehydroabietyl imidazoline (IV) has been developed. A solution of dehydroabietic acid (I) in xylene used as water-carrying agent was dropwise added to the hot diethylenetriamine (DETA) to give the product via a high temperature liquid-liquid-short-contact dehydration condensation reaction. The product has a poor solubility in DETA, which is used as the reactant and can regulate reaction temperature; the water produced by dehydration condensation was easily taken out of the reaction system by xylene, which was fast heated and evaporated. The product was easily separated from reaction mixtures via cool crystallization, and structurally identified by means of EA, IR, UV, 1H-NMR and 13C-NMR. Molar ratio of DETA to compound I could change the reaction temperature, which has obvious effect on the yield and color of the product. Under the reaction conditions ( amount of compound I, 30 m mol; molar ratio of DATE to compound I , 15.7; reaction temperature, 210 ℃; reaction time, 4 h),the yield is 86.0 %.