2-Alkylimidazolines were prepared from organic acid including n-pentanoic acid, n-hexanoic acid, lauric acid, stearic acid and 1,2-ethylanediamine by pressure-fractionation method，respectively.The target compounds’ chemical structures were characterized by 1HNMR and FT-IR.The results showed that the preferred synthetic conditions were as following: n(organic acid):n(1,2-ethylanediamine)=1:5,reaction at 185℃ and fraction at 155℃ under the pressure of 0.25MPa.The 2-alkylimidazolines were obtained with high purity and excellent yield(86%～98% based on organic acid).