The present invention is related a square packed tower for collection of flue gas CO2. The square packed tower comprises an initial absorbent distributor on the lower end of the flue gas outlet, a vertical plate packer on the lower end of the initial absorbent distributor and a radial diversion gas distributor at the bottom of the square packed tower for delivery of carbon dioxide contained in the flue gas. The radial diversion gas distributor comprises a gas inlet pipe, a butterfly base plate, a butterfly seal plate and numerous radial deflectors. The butterfly base plate is connected with outlet of the gas inlet pipe. The radial deflectors are in radial arrangement between the butterfly base plate and butterfly seal plate along the outlet of gas inlet pipe.