The surface chemical composition and microstructure of walnut protein obtained through aqueous buffer and bis(2-ethylhexyl) sodium sulfosuccinate (AOT) reverse micelles were determined by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The surfaces were characterised by XPS to monitor surface composition. The different components of C 1s, N 1s and O 1s peaks were provided precisely. By comparison with walnut protein surface from aqueous buffer, XPS analysis revealed that the O atomic percentage of walnut protein powder surface from AOT reverse micelles was higher, but the C and N atomic percentages were lower. The N/C ratio of the walnut protein powders using two extraction methods was similar, while significant difference was obtained in the O/N. The obtained results indicated that the reverse micelles could affect the C, O and N components on the surface of walnut protein powder. Protein microstructure after reverse micelle treatment showed many crystals.