Novel Ni--Cr nanocomposite coatings were fabricated by composite electrodeposition of Ni and Cr nanoparticles from a nickel sulfate bath. The influence of the Cr contents in nanocomposite film was investigated by changing Cr concentration in electrolyte bath, agitation rate and current density. Surface morphologies and microstructure of Ni--Cr coatings were observed by means of SEM / EDAX, TEM and XRD. It was found that the codeposition of Cr nanoparticles disturbed the crystal growth of the nickel matrix, leading to a change from the preferential Ni on （200） planes to the homogeneous growth on （200）, （111） and （220） planes. This demonstrated that the nanoparticles codeposition promoted the nucleation of new nickel grains. The more the content of the Cr nanoparticles codeposited, the finer the electrodeposited Ni matrix. Meanwhile, the electrodeposition mechanism of the Ni--Cr nanocomposite system was discussed.