The balanced foam proportional mixing device feeds the pressure supplied by the foam liquid and the pressure water to the balance valve through the foam liquid pump, and automatically adjusts the valve switch size to achieve dynamic balance. Put a certain amount of foam liquid and pressure water into the proportional mixer to form a foam mixed liquid. If the ratio of pressure and flow in the water inlet pipe is unstable, the balance valve adjusts the amount of foam liquid through dynamic balance and then enters the proportional mixer to make the ratio of the foam mixture accurate. It can add foam liquid during operation to prolong the fire extinguishing time. Improve the ability of fire fighting and disaster resistance. Applicable to important fire protection projects such as large petrochemical enterprises, oil depots, docks and offshore drilling platforms.