Gypsum retarder is an important additive of building materials. Commercial gypsum retarders are mainly composed of four types: organic acids, phosphates, protein and composite retarder. Although the effects of organic acids and phosphates have better retarding performances, there is still obvious a shortcoming that the mechanical strength reduces largely with time going by. Protein based retarders prolong the setting time of hemihydrates with less strength loss and higher costs. The gypsum retarder from waste mycelium, a protein-rich raw material, solved the problem of the disposal of waste mycelium from anti-biotic plants, while producing high-quality retarder for gypsum, shows potential for future.