The utility model describes a heat treatment furnace, comprising an internal cover of the furnace, a furnace platform, a bottom board of the furnace, and a supporting seat for the bottom board of the furnace. the internal cover of the furnace is covered on the furnace platform, a bottom board of the furnace is provided on the supporting seat, a plurality of convection slots are spacedly provided on the lower surface of the bottom board of the furnace. compared with the prior art, the utility model has beneficial effect is that the convective slot performs convective heat transfer in order to accelerate the heat transfer. a carbon steel bottom board of the furnace with convective slot is used substitution of furnace bottom boards in heat resistant steel or heat resistant alloy in the prior art, a supporting seat in flame retardant material is used in substitution of heat resistant steel cylindrical support in the prior art. the utility model is capable of evidently improving heat conduction contact surface of workpiece, improving temperature uniformity and heating efficiency in the furnace. cost of material can be greatly reduced and energy can be greatly saved by using carbon steel bottom board of the furnace, and life of the furnace bottom board is prolonged.