The present disclosure relates to a pneumatic serial device for spraying materials into a deep soil layer and an implementation method thereof. The device comprises a material spraying injector (1), a air blasting system (2) connected with the material spraying injector (1), and a material feeding system (3), wherein the air blasting system (2) and the material feeding system (3) are connected with the material spraying injector (1) in series in sequence, wherein the air blasting system (2) comprises a high-pressure air tank (2-1) and a quick relieve valve (2-2), the material feeding system (3) comprises a material chamber (3-1), a feeding valve (3-2), a valve I (3-3), a material sending chamber (3-4), a valve II (3-5) and a material delivery pipe (3-6) which are connected to each other in sequence, and the material delivery pipe (3-6) extends into the high-pressure air tank (2-1) and is communicated with the quick relieve valve (2-2) at the bottom thereof. Combined with the implementation method thereof, the device can uniformly apply a certain amount of various materials into the soil layer at any depth, replacing the traditional method, greatly improving the operation efficiency of applying materials into the deep soil layer, significantly reducing the cost of applying materials into the deep soil layer, and reducing the labor intensity.