The utility model relates to a mixer and one -way return -air device thereof, the mixer including the stirring chamber, be provided with one -way return -air device on the stirring chamber, one -way return -air device includes one -way air return valve, be connected with the intercommunication passageway between one -way air return valve and the stirring chamber. The powder is guaranteed and weighs the precision that it is controllable to guarantee that the trueness error is weighed to the powder, guarantees concrete quality and building engineering's quality safety to this one -way air return valve's the inside problem that has the negative pressure of mixer during operation in the conventional art that has set up effective solution.