The work aims to understand the effects of chromium content on morphology of boride and wear resistance of surfacing alloy by adding different content of chromium to Fe-xCr-3.5B-0.1C flux cored wires. Fe-Cr-B wear-resistant alloys were prepared on Q235 steel substrate by flux-cored wire arc welding. The microstructure and composition of surfacing alloy layer were analyzed by optical microscopy (OM), X-ray diffractometer and scanning electron microscopy. Abrasive wear test of the surfacing layer was conducted by grain-abrasion testing machine with wet sand rubber wheel. Fe–3.5B–xCr (x=9, 12, 15, 20 wt. %) alloys were mainly composed of dendrite ferrite, martensite, pearlite and borides. With increase of Cr content, boride transformed from Fe2B to (Cr,Fe)2B and was mainly distributed in the net or fishbone structure in the metallic substrate. When the chromium concentration exceeded 9 wt.% during solidification process, primary (Cr,Fe)2B particles formed, and then eutectic M2B and Fe-based BCC solid solution formed. The eutectic microstructure mainly consisted of the substrate and long striped M2B boride. The atom fraction ratio indicated that the borides changed from Fe2B→(Fe, Cr)2B→(Cr, Fe)2B. Cr content had significance to structure and boride morphology of Fe-Cr-B wear-resisting surfacing alloy. Microhardness of boride improved gradually as Chromium atoms entered Fe2B due to spatial structure change of boride. With the increase of Cr content, hardness and wear resistance of surfacing alloys show a trend of continuous improvement. Provided with Cr content as 20 wt.%, M2B phase is randomly embedded in the matrix as the wear-resistant framework and the wear resistance increases by about 7.4 times compared with that containing 9 wt.% Cr.