The invention relates to a gas-liquid two-phase uniform distribution device of a plate fin heat exchanger. The device is characterized by comprising a liquid injecting seal arranged in a core internal runner of the plate fin heat exchanger; a gas-phase inlet seal is arranged at the end part of a core of the plate fin heat exchanger, and is provided with a gas-phase connecting pipe; liquid-phase inlet seals are respectively arranged on two sides of the outer wall of the core of the plate fin heat exchanger, and are respectively provided with liquid connecting pipes; one liquid connecting pipe is provided with a pressure difference valve; the liquid injecting seal includes a liquid-phase groove and a gas-phase groove; two ends of the liquid-phase groove are communicated with the two liquid connecting pipes; one end of the gas-phase groove is connected with the pressure difference vale through a gas-phase signal pipe; the other end of the gas-phase groove is a closed end; multiple through holes are formed in the side walls of the liquid-phase groove and the gas-phase groove at intervals; one side of the liquid injecting seal is tightly connected with the inner wall of the core of the plate fin heat exchanger; and a gap is formed between the other side of the liquid injecting seal and the corresponding inner wall of the core internal runner of the plate fin heat exchanger to form a medium channel.