The invention provides a method for producing a protein foam concrete foaming agent by sludge, which comprises the following steps of: adding 5-6 percent of lime into sludge containing protein; carrying out high-temperature hydrolysis for 1-2 hours in a reactor; filtering and removing slag to obtain a protein solution mixture; concentrating, and then adding 0.1-0.2 percent of protective agent and adding 3.0-3.6 percent of xanthan gum to prepare the sludge protein foam concrete foaming agent. The foaming agent has the expansion rate of foam more than 50 and the stable time more than four hours and achieves the production requirement. After foaming, the foaming agent is added with No. 42.5 cement, perlite, pulverized fuel ash and water to be uniformly mixed and can be directly used as heat insulation materials of a roof, an inner wall and an outer wall and a filling material in construction or after foaming by an air tank, the sludge protein foam concrete foaming agent is uniformly mixed with rapid-hardening sulphoaluminate, the pulverized fuel ash, a fiber and water; and a sludge protein foam concrete energy-saving plate or a sandwich plate and a sound insulating material used for a high-rise building wall or a high-noise environment can be prepared in the processes of casting and maintenance.