The invention discloses a primary air ejection structure of a device for treating waste gas of a rotary kiln and a process. The device comprises a high-temperature waste gas cooling device, a primaryair ejection device and a throat mixing area; a waste gas channel of the high-temperature waste gas cooling device communicates with a waste gas channel of the primary air ejection device; the waste gas channel of the primary air ejection device is connected with the throat mixing area; a primary air inlet of the primary air ejection device is connected with a tubular heat exchanger of the high-temperature waste gas cooling device; a pipe pass outlet of the tubular heat exchanger of the high-temperature waste gas cooling device is connected with a heat primary air pipe of the primary air ejection device; a primary hot air nozzle of the primary air ejection device is positioned on a central shaft of the primary air ejection device, and is aligned to the throat mixing area; and the throat mixing area is of a shrinkage and diffusion structure. Waste gas is treated as safe waste gas containing no combustible matter according to process requirements and waste gas components, so that heat generated by the waste gas after combustion can be recovered by such heat recovery equipment as an afterheat boiler, and meanwhile, qualified emission is guaranteed.