An alkaline protease was used to catalyze the hydrolysis of gelatin to prepare base solution of the foaming agent, and it was compounded with sodium dodecylbenzenesulfonate and fatty alcohol polyoxyethylene ether sodium sulfate to prepare a variety of new protein-based foaming agents. These foaming agents were preselected based on the foam indexes, and then air-foam treated lightweight soil samples were prepared using these foaming agents. Then the densities of these samples were measured. According to foam indexes and sample densities, the best foaming agents are the homemade foaming agent F-6 (10% gelatin, 11.4% sodium dodecylbenzenesulfonate, 12.6% fatty alcohol polyoxyethylene ether sodium sulfate ) and F-7 (10% gelatin, 7.8% sodium dodecylbenzenesulfonate, 15.4% fatty alcohol polyoxyethylene ether sodium sulfate). The 1 hour defoaming ratio of these two foaming agents is 52.52% and 53.18%, respectively, and the foaming multiples are 82.61 and 81.66, respectively. The comprehensive performance of these two foaming agents is better than that of general commercially available foaming agents, and the densities of the samples were relatively small.The compressive strength can reach 4MPa, fully meeting the engineering requirements.