The present invention relates to an alternate foam storage and proportionally mixing device, comprising at least one normal pressure foam storage tank (12), at least two pressure foam tanks (1,1a) at least one proportional mixer (2) and a control unit, wherein the foam storage tank (12) is used to store foam liquid and alternatively output the foam liquid to the at least two pressure foam tanks (1,1a), and the at least two pressure foam tanks (1,1a) alternatively output the foam liquid to the at least one proportional mixer (2), and the at least one proportional mixer (2) outputs mixed foam liquid. The alternate foam storage and proportionally mixing device has the advantages of accurately mixing foam liquid, simple structure, and rubber diaphragm that tends not to be broken. As a major component of the present invention, the pressure foam tank (1,1a) may be produced in a standard manner, thereby greatly reducing production cycle and cost.