Boronized layer was prepared on silicon steel substrate by pulse electrodeposition in KCl-NaCl-NaF-Na2B4O7 molten salts with different current density. The effect of current density on composition and microstructure of boronized layer was studied. The phase, the cross-sectional morphology and the compositional depth profile of the layer were studied by X-ray diffraction analysis (XRD), optical microscopy (OM) and glow discharge spectrometry (GDS). The presence of FeB on the surface of the boronizied steel was confirmed by XRD analysis. Cross sectional observation revealed that the boronized layer consisted of the outer layer FeB and the sublayer Fe2B. In addition, the low current density produced more proportion of Fe2B and bigger saw-tooth grains.