Promoted Cu-Fe3O4 catalysts for water gas shift (WGS) reaction are synthesized via an aerosol-spray self-assembly (ASSA) method. The structure changes of fresh, reduced and used catalysts are characterized by multiple techniques including scanning and transmission electron microscope (SEM and TEM), ex-situ/in-situ X-ray diffraction (XRD) and N2-adsorption. By using temperature-programmed reduction (TPR) under different atmospheres (H2/CO) and X-ray photoelectron spectroscopy (XPS), the interaction between Cu and Fe species has been confirmed, and highly dispersive Cu0 has been further identified as the active phase. The Cu-Fe interaction helps stabilize and greatly improve the dispersion of Cu0 and thus enhances the WGS conversion. The addition of Fe also facilitates the adsorption of CO and H2O, as demonstrated by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) of in-situ mode. The Cu0.3Fe0.7Ox catalyst exhibits very high catalytic activity and a tri-component Cu-Fe3O4-Al2O3 catalyst shows even better WGS conversion and stability.