In order to expound the influence of interactions between organic alkali ethanolamine and crude oil fractions in Shengtuo 28 block crude oil on the interfacial tension, the crude oil fractions (saturates, aromatics, resins and asphaltenes) were obtained by classic SARA method. The acidic components were extracted from Tuo 28 block crude oil by using NaOH/EtOH mixed solution. The dynamic interfacial tensions between all crude oil fractions and ethanolamine were investigated by means of Spinning Drop method. The experimental results show that the key factors of reducing interfacial tension between organic alkali and model oils are the content and structure of petroleum acids. The minimum value of dynamic interfacial tension can reach 10-2 mN/m order of magnitude. The higher the content of petroleum acid is, the longer the low transient value of interfacial tension keeps. The order for the ability of Tuo 28 crude oil fractions to react with ethanolamine is: acidic components are the strongest; resins are next; asphaltenes, aromatics, and saturates are the weakest.