The invention belongs to the technical field of building materials and provides an energy-saving brick prepared from sludge of a sewage treatment plant and a preparation method. The energy-saving brick prepared from the sludge of the sewage treatment plant comprises the following components in parts by weight: 42-56 parts of sludge of the sewage treatment plant, 12-16 parts of Chinese herbal medicine, 6-19 parts of quick lime, 6-13 parts of oyster powder, 1-7 parts of early strength agent, 1.05-3.07 parts of water reducer, 3-15 parts of fire retardant and 7-18 parts of water. The invention aims to provide the energy-saving brick prepared from the sludge of the sewage treatment plant and solves the problem of sludge recycling. According to the preparation method for the energy-saving brick prepared from the sludge of the sewage treatment plant provided by the invention, the production period is reduced, sintering is not required, no heat energy is required, time is saved, production rate is increased, production cost is lowered and the problem of secondary pollution caused by improper sludge treatment is relieved.