The invention relates to a method for controlling combustion atmosphere in a large-scale walking beam type plate blank heating furnace, which belongs to the technical field of fuel combustion of industrial furnaces. A plate blank is heated through a preheating section, each heating section and a soaking section to finish the process of heating and temperature equilibrium; and in the process, a first-level computer control system and a second-level computer control system automatically generate a heating process and automatically set and control the furnace temperature in each section according to original data of the plate blank called from a database; and on the basis of an output control value of a residual oxygen analyzer, the computer control systems calculate the air consumption coefficient of each combustion area, perform dynamic track on the combustion atmosphere in the whole furnace along with the changes of thermal loads, correct the combustion atmosphere according to the actual air-fuel ratio of six combustion areas, adjust the proportion of combustion air and gas, and determine the reasonable air and gas flow to achieve the furnace temperature required by the heating process. The method has the advantages that the condition of furnace gas component changes in the furnace is quantificationally provided for a heating furnace operator in time, so that the combustion in the heating furnace reaches good state; and simultaneously, the energy-saving and environmental protection effects are remarkable.