A foam production method includes mixing liquid nitrogen with a foaming material to produce foam. A gas is produced in situ from liquid nitrogen. As the ratio of the volume of the gas produced by gasification of liquid nitrogen to the volume of the liquid nitrogen is relatively high, when a large gas supply flow is needed to generate a large foam flow, a liquid nitrogen storage device of a small volume can be used instead of bulky air supply devices such as high-pressure gas cylinders, air compressors, air compressor sets and the like, reducing the volume of the air supply device. In addition, the liquid nitrogen used in foaming will release nitrogen gas after the foam blast, such that the nitrogen is also able to inhibit combustion on the surface of burning materials, accelerating the extinguishing of the fire.