A method for high yield foaming of coffee, characterized by comprising: in a first step, providing a pressure control mechanism connected with a gas pressure source at an inlet of the pressure control mechanism and connected with a water reservoir at an outlet of the pressure control mechanism , brewing water being contained in the water reservoir , a coffee placement cavity being arranged below the water reservoir , with a bag of coffee placed in the coffee placement cavity , a back pressure resonance mechanism being arranged below the coffee placement cavity , and a coffee outlet being arranged at a lower part of the back pressure resonance mechanism ; in a second step, then pressing down a button , the pressure control mechanism decompressing high-pressure gas of the gas pressure source to a gas having a brewing pressure which enters the water reservoir , water having the brewing pressure then entering the coffee placement cavity to be mixed with the coffee and extracted; and in a third step, coffee slurry then entering the back pressure resonance mechanism , first arrival coffee slurry flowing down from a guide hole of a guide plate and entering an annular space , at the moment a cartridge bottom surface of a back pressure cartridge being pressed by a colloid ring , one resonance needle being arranged and placed on the cartridge bottom surface , a resonance groove being arranged at a contact position of the colloid ring with the resonance needle , the resonance groove being buckled on the resonance needle to constitute a resonance cavity , when the coffee slurry having the brewing pressure passes through the resonance cavity , due to the brewing pressure and a special structure of the resonance cavity constituted between the resonance groove and resonance needle , the coffee slurry having the brewing pressure being sufficiently foamed after high-frequency oscillation and flowing out of the coffee outlet . in a first step, providing a pressure control mechanism connected with a gas pressure source at an inlet of the pressure control mechanism and connected with a water reservoir at an outlet of the pressure control mechanism , brewing water being contained in the water reservoir , a coffee placement cavity being arranged below the water reservoir , with a bag of coffee placed in the coffee placement cavity , a back pressure resonance mechanism being arranged below the coffee placement cavity , and a coffee outlet being arranged at a lower part of the back pressure resonance mechanism ; in a second step, then pressing down a button , the pressure control mechanism decompressing high-pressure gas of the gas pressure source to a gas having a brewing pressure which enters the water reservoir , water having the brewing pressure then entering the coffee placement cavity to be mixed with the coffee and extracted; and in a third step, coffee slurry then entering the back pressure resonance mechanism , first arrival coffee slurry flowing down from a guide hole of a guide plate and entering an annular space , at the moment a cartridge bottom surface of a back pressure cartridge being pressed by a colloid ring , one resonance needle being arranged and placed on the cartridge bottom surface , a resonance groove being arranged at a contact position of the colloid ring with the resonance needle , the resonance groove being buckled on the resonance needle to constitute a resonance cavity , when the coffee slurry having the brewing pressure passes through the resonance cavity , due to the brewing pressure and a special structure of the resonance cavity constituted between the resonance groove and resonance needle , the coffee slurry having the brewing pressure being sufficiently foamed after high-frequency oscillation and flowing out of the coffee outlet . <EOS>