AbstractBoth alkylketene dimer (AKD) and alkenyl succinic anhydride (ASA) are widely used neutral papermaking sizing agents. However, AKD has the issue of sizing hysteresis, while ASA requires on-site emulsification. In addition, both reagents are readily hydrolyzed. Di-(stearylamidoethyl) epoxypropyl ammonium chloride (DSEAC) has been applied as a fabric softener, but it is a potential sizing agent which leads to good sizing without sizing hysteresis. It could be synthesized by a two-step process starting from stearic acid and diethylenetriamine. During the process, the stearamide structure obtained from the first step plays a key role in the second process as well as sizing. This paper focuses on the impact of the synthetic process of the first step on the structure and sizing properties of DSEAC. Single factor experimental results demonstrated that the optimal temperature should be 160 °C while the optimal reaction time should be less than 3.5 hours. Orthogonal analysis experiments indicated that the optimal synthetic process was maintaining 100 °C for 30 min, and then increasing the temperature to 160 °C for 3.5 hours. Dosages of the catalysis and antioxidant were 0.5% and 0.6% of stearic acid, respectively.