Boronized layer on silicon steel substrate was fabricated using pulse electrodeposition technique with different duty cycle in KCl-NaCl-NaF-Na2B4O7 molten salts. The effect of the duty cycle on composition and microstructure of obtained layer was investigated. The boronized layer was analyzed by X-ray diffraction analysis (XRD), optical microscopy (OM), glow discharge spectrometry (GDS), and atomic force microscopy (AFM). The results showed that in the range of 10-50%, duty cycle almost had no effect on composition and thickness of the layer. The boronized layers in this range exhibited FeB phase on the surface of silicon steel. However, duty cycle had great effect on the microstructure of the boronized layer. A fine grain size boronized layer can be obtained at a duty cycle of 20%.