The invention belongs to chemical heat treatment technology of novel gear steel, and particularly relates to a 9310 steel carbon-nitrogen co-permeation method. The 9310 steel carbon-nitrogen co-permeation method comprises the following steps that the part is 9310 steel, the part is subjected to thermal refining, and then the part is placed in a controllable atmosphere nitriding furnace for carbon-nitrogen co-permeation, wherein the carbon-nitrogen co-permeation is divided into two stages, namely a first stage, the carbon potential is 0.30%-0.40%, the carbon-nitrogen co-permeation time is 30-40min, the carbon potential in a second stage is 0.95%-1.05%, the carbon-nitrogen co-permeation time is 0.5h-3 h, and meanwhile, the co-permeation temperature of the two phases is 840 +/-10 DEG C, theammonia gas flow rate is 0.3-0.6m<3>/h, and cooling and tempering are carried out. According to the method, the depth of a shallow infiltration layer of the 9310 steel can be effectively controlled, and the toughness and the surface hardness of the 9310 steel can meet the design requirements; and meanwhile, the method is simple in process, convenient to operate and easy to implement.