The invention discloses a metal expansion joint inner surface FEP electrostatic powder spraying process in the technical field of spraying processes. The process comprises the steps of (S1) substrate selection, (S2) polishing, (S3) high-temperature oil removal, (S4) sand blasting and cleaning, (S5) spraying material preparation, (S6) preheating, (S7) primer spraying and drying, (S8) finish coat spraying, (S9) high-temperature sintering, (S10) repeated spraying and sintering, (S11) detection and treatment and (S12) cleaning and packing; Teflon paint of fluorine paint with polytetrafluoroethylene as basal body resins is adopted, so that the excellent characteristics of metal expansion joints are improved, the service life of the metal expansion joints is prolonged, the paint spraying operation is simple, and the paint spraying is uniform; through previous polishing, high-temperature oil removal, sand blasting and cleaning, impurities and dust on the inner surfaces of the metal expansion joints are effectively removed, so that the sand blasting roughness is improved; and through later finished product appearance detection, coating film thickness detection, electrospark detection and adhesion detection, the inner surfaces of the metal expansion joints thickly sprayed are detected by multiple times, so that the coating quality is improved.