Plasma electrolytic boriding (PEB) technology is an effective way to form iron borides on the steel surface. Compared with the single boriding process, the multi-element boriding process can further effectively reduce the hardness gradient by forming a transition layer containing C and N elements between the boride layer and the steel substrate, which plays a significant role in improving the performance of the diffusion layer. At present, the evaluation of the corrosion resistance of the boride layer on metal surface is mostly carried out under static corrosion conditions. However, the metal workpiece is more vulnerable due to corrosion and friction interaction in corrosive medium and long-term mechanical operation environment, so studying the tribo-electrochemical behavior of metal in corrosive medium environment is critical. In this work, the plasma electrolytic borocarbonitriding process (PEB/C/N) was carried out in an aqueous solution containing 25wt.% borax, 10wt.% glycerin and 3wt.% carbamide. The anode and cathode were set to be the stainless steel bath and the Q235 low-carbon steel sample, respectively. The constant negative bias voltage was increased to 280 V, and the whole processing time was 30 min. The morphology, composition distribution and phase composition of the borocarbonitriding layer were studied. The tribo-electrochemical behavior of Q235 steel substrate and PEB/C/N sample against Si3N4 ball in 3.5wt.% NaCl solution was evaluated by electrochemical open-circuit potential (OCP) tests and tribological tests. The results showed that the electron temperature in the plasma zone around the sample was stable at 3 500 K in the PEB/C/N process at 280 V. After the PEB/C/N treatment for 30 min, the borocarbonitriding layer contained a 15 μm surface layer which was mainly composed of Fe2B phase and a 40 μm transition layer. In friction, the open-circuit potential of PEB/C/N sample remained between ?200 mV and ?300 mV with a small fluctuation, which was obviously higher than the Q235 steel substrate. The corrosion resistance of the PEB/C/N sample was significantly improved. Meanwhile, the wear rate of the PEB/C/N sample was 3.88×104 μm3/(N×m), which was only 1/3 of the Q235 steel substrate, and the wear resistance of the PEB/C/N sample was obviously improved. In the NaCl solution, dislocation increment and migration in plastic deformation occurred on bare Q235 steel due to the interaction of corrosion and wear. There were intensive parallel furrows and obvious fatigue spalling on the wear surface of the Q235 steel substrate, so the wear mechanism of Q235 steel substrate was mainly fatigue and abrasive wear. However, the borocarbonitriding layer of the PEB/C/N sample effectively prevented the corrosion of Cl?on the Q235 substrate. Therefore, the surface damage of the PEB/C/N sample was mainly caused by friction and wear factors in tribo-electrochemical experiments. When the local area of the surface boride layer was destroyed by the Si3N4 friction pair, some abrasive particles with high hardness were ground off, and the wear surface of the PEB/C/N sample presented sharp and narrow furrows, so the wear mechanism of the PEB/C/N sample was mainly abrasive wear.