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 N-2-adsorption. By using temperature-programmed reduction (TPR) under different atmospheres (H-2/CO) and X-ray photoelectron spectroscopy (XPS), the interaction between Cu and Fe species has been confirmed, and highly dispersive Cu-0 has been further identified as the active phase. The Cu-Fe interaction helps stabilize and greatly improve the dispersion of Cu-0 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.