The invention discloses a total recycling method and system for diffused fuel gas in a material tank at the top of a blast furnace. Two recycling stages including a high-pressure fuel gas recycling stage and a low-pressure fuel gas recycling stage are adopted according to the air pressure size of the diffused fuel gas in the material tank. High-pressure diffused fuel gas in the material tank is directly recycled into a fuel gas pipe network by virtue of free gas pressure difference between the diffused fuel gas in the material tank and the fuel gas pipe network in the high-pressure fuel gas recycling stage; the diffused fuel gas in the material tank is jet by virtue of an ejector in the low-pressure coal gas recycling stage, primary pressure-sharing fuel gas in the material tank or secondary pressure-sharing nitrogen in the material tank is taken as an ejecting source, the polluted fuel gas is not recycled, the ejector adopts a non-negative pressure ejecting manner, and the low-pressure fuel gas recycling stage is stopped when air pressure of the diffused fuel gas in the material tank is decreased to 100Pa-200Pa, so that the malignant accident of the ejector caused by that a negative pressure is formed in the material tank due to excessive ejection and then air enters the material can be avoided.