Plasma electrolysis is one of the methods for high-speed electrochemical and thermal treatment of metals and alloys. Plasma electrolytic saturation (PES) of low-carbon steels by light elements from aqueous solutions (e.g. PEC, PEN/C, hardening, etc.) is of particular interest. The possibility of anode plasma electrolytic borosulfonitrocarburizing (PE BSN/C) and boronitrocarburizing (PE BN/C) was the purpose of present research. Multicomponent saturation with carbon, nitrogen, boron and sulfur enables to expand the range of obtained properties with simultaneously reducing the processing time. Moreover, preliminary preparation of workpiece is not needed. Furthermore, local treatment by dipping or by spraying is possible. Finally, rounding of borders and removal of slivers take place The process was realized in a working chamber with a longitudinal electrolyte flow around through a pipe located at the bottom of the chamber. The cylindrical samples (height 15 mm, diameter 12 mm) of steel 20 (0.17–0.37 Si, 0.35–0.65 Mn, 0.25 Cu, 0.25 Ni, 0.04 S, 0.17–0.24 C, 0.035 P, 0.25 Cr, 0.08 As wt. %) were treated  in aqueous electrolyte on the base of ammonium chloride (15 wt. %), carbamide (15  wt. %), boric acid (10 wt. %) and sodium thiosulfate (10 wt. %) in the case of PE BSN/C. PE BN/C was carried out in aqueous solution with ammonium chloride (15 wt. %), carbamide (15 wt. %) and boric acid (5 wt. %). The heating temperature of the workpieces was regulated by varying the DC voltage (150–300 V) and ranged from 650 to 950 °C. The treatment time of each workpiece was ranged from 2 to 10 minutes. Cooling after treatment was carried out in electrolyte (with hardening). The phase characteristics of saturated surface layers were determined by means of Zeiss Supra 40 field emission scanning electron microscope with INCAx-act X-ray detector (Oxford Instruments). The surface layer structure was studied using ЕС МЕТАМ РВ-21 optical microscope after grinding, polishing and etching of metal grain boundaries. The surface layer thickness was measured similarly by microscope. Microhardness distribution in the surface layer was determined by a Vickers hardness tester equipped with diamond indenter with a load of 50 g. Rockwell hardness (HRC) was measured according to GOST 9013-59 (Russian State Standard). The tensile strength and impact test were carried out according to GOST 1497-84 and GOST 9454-78, respectively. Metallographic analysis was showed structure of the treated steel surface. It is composed of alternating of oxide and diffusion layers. Oxide layer thickness 45 mkm is obtained by increasing temperature of PE BSN/C to its maximum – 800 ^oC. EDX-analysis detects carbon concentration 0,8 wt.%. under the oxide layer. The concentrations of nitrogen, boron and sulfur are 0.3-0.4 wt.%. The content of diffusive elements in the surface layer is sufficient for austenitizing of steel with forming of martensite in a layer thickness 35 mkm. Microhardness distribution in the diffusive layer corresponds to its phase composition: the highest value is observed at the edge of the surface and further down into the sample. The maximum microhardness 600 HV is reached at the treatment temperature 800 ºC.  Thickness of the oxide layer at PE BN/C grows in range of 650-900 °C from 36 to 108 mkm. Diffusion layer thickness reaches 90 mkm after treatment at 850 °C. The highest microhardness of the diffusion layer (to 830 HV) achieved at lower temperature (800 °C) in comparison with traditional boriding and carburizing (more than 900 °C).