The invention discloses a method for removing nitrogen and phosphorus from water by using calcium silicate prepared from silicon recycled from red mud, and relates to a method for removing nitrogen and phosphorus from water. By the method, the problems of waste resource utilization and removal of excess nitrogen and phosphorus from water are solved. The method comprises the following steps: leaching most of metal oxides from the red mud by using dilute hydrochloric acid first and then leaching titanium and rare earth elements from the red mud by using concentrated sulfuric acid so as to leave silicon dioxide powder, and then preparing the extracted silicon dioxide into calcium silicate by a hydrothermal method. A certain amount of calcium silicate is added into waste water containing nitrogen and phosphorus, the waste water is oscillated at a certain temperature, ammonia nitrogen is removed from water through gas-liquid separation, and phosphorus is removed from water through ligand exchange and chemical precipitation.