Hydroxyethyl ethylenediamine(AEEA) was synthesized from ethylenediamine(EDA) and ethylene oxide(EO) by ethoxylation in a continuous flow microreactor with special microstructure. The effects of material ratio, water content of ethylenediamine, reaction temperature and residence time on the reaction were investigated. The optimal process conditions were determined: n(EDA): n(EO) = 3:1, the water content of ethylenediamine should be controlled within 5% (mass fraction), reaction temperature was 80 °C, and residence time was 60 s. Under these conditions, the conversion of EO is close to 100%, the selectivity of AEEA was 87.4% and the selectivity of dihydroxyethyl ethylenediamine was 9.2%. In the batch kettle reactor, the selectivity of AEEA is 83.5% and the selectivity of dihydroxyethyl ethylenediamine is 15.9% under the same material ratio and reaction temperature. Compared with that, the continuous flow microreactor can effectively improve the selectivity of AEEA, reduce the occurrence of side reactions, greatly shorten the reaction time and improve the reaction efficiency.