Combined flat tempering furnace of LD-AT series has two heating zones arranged in sequence. According to the process requirements, its heating manner may be a free combination of convection and radiation. According to the quality requirements of the products, its cooling part may consist of one or more air grids. A variety of combination manners and operating modes of the equipment form different performance characteristics of the combined tempering furnace, which can most precisely meet the requirements on products of different users .