To improve the emulsification of whey protein isolate (WPI), the lotus root amylopectin (LRA) was conjugated to WPI by dry-heat reaction, giving the WPI-LRA complex. In order to obtain a WPI-LRA complex with good emulsification property, response surface methodology was employed to optimize the reaction condition. Results showed that the maximum emulsifying activity (EA, 73.8%), emulsifying stabilities (ES, 72.58%) were achieved when the reaction temperature, reaction time and LRA addition volume were fixed at 44 °C, 13.6 h and 24%, respectively. In addition, the physicochemical properties of WPI-LRA O/W emulsions were assessed under different pH, NaCl concentration and storage time. Results showed that there are significant effects of pH and NaCl on the emulsification capacity of WPI-LRA conjugate. Moreover, compared to the WPI, the WPI-LRA conjugate can enhance the physicochemical properties of O/W emulsion. In conclusion, the WPI-LRA conjugate generated by dry-heat reaction is a new emulsifier with good emulsifying properties, which has good potenial for the application in functional foods.