Abstract: In order to understand the effect of covalent graft modification of protein on its emulsifying stability, WPI-EGCG graft was prepared by free radical grafting using whey protein isolate (WPI) and epigallocatechingallate (EGCG) as raw materials. Scanning electron microscopy (SEM) was used to observe the microstructure, and the effect of covalent grafting on the interface stability was investigated by measuring the adsorption capacity of interfacial protein and the rheological properties of the interface. Lycopene nano-emulsion was constructed by WPI-EGCG graft as emulsifier, and its physicochemical stability and storage stability were studied. The results showed that the free radical grafting of EGCG changed the structure of WPI and made it higher viscosity and interfacial stability, so that the lycopene nano-emulsion system using the graft as emulsifier had higher physical and chemical stability. The size and ζ-potential of the WPI-EGCGE graft-stabilized lycopene nano-emulsion increased 268.3 nm and 17.6 mV, respectively, after 30 days of storage at 37 ℃. The retention rate of lycopene in the emulsion was 66.23%, showing a better lycopene protection effect. This study would provide a reference for the construction of nano-emulsion transport system of functional active substances.