The boride layers were fabricated on Q235 low-carbon steel by duplex plasma electrolytic saturation treatment in order to improve the boriding efficiency. The two-step process for plasma electrolytic carburizing (PEC) with 5 min and plasma electrolytic borocarburizing (PEB/C) with 5 min-15 min was applied. Their microstructure, hardness, corrosion and wear behaviors were analyzed. XRD and XPS spectra confirmed that the modified boride layers consisted mainly of Fe2B phase. The thickness of the borided layers for combined PEC + PEB/C treatment increased considerably comparing to PEB/C treatment alone. The PEC pretreatment can enhance the growth of boride layer for the following PEB/C process. The corrosion resistance and wear resistance of Q235 low-carbon steel with combined PEC + PEB/C treatment were also significantly improved. In addition, by increasing the PEB/C time from 5min to 15min, the hardness, corrosion and wear resistance of boride layer on PEC + PEB/C samples increased. The main reason was that the thickness and Fe2B phase content of boride layer increased.