The influence of the O-doped behavior on the superhard Pmm2-BC2N is investigated by using the first-principles hybridization functional calculation. The mechanical stability and the thermal stability of all considered structures are examined by elastic constants and molecular dynamics simulations, respectively. Furthermore, the feasibility after the doping behavior is examined with the formation energy. The optical and mechanical properties of the pristine and the O-doped Pmm2-BC2N are calculated. The results demonstrate that all the O-doped structures are stable, and O@C-2 and O@N have lower formation energy, indicating that they are easier to be synthesized. It is found that the N substituted by O atom can obviously improve the absorption in the visible light range. The calculated Vickers hardness demonstrates all the considered structures are superhard. Especially, the O@N structure is a potential functional material with the satisfactory hardness and absorption in visible light range.