The invention provides an intelligent informationized drainage system of a building. The intelligent informationized drainage system comprises a water distribution tank, a blowdown tank, a water storage tank and a control system, wherein the water distribution tank is arranged at the top of the building; the blowdown tank and the water storage tank are arranged on the ground; the water distribution tank is connected with the blowdown tank through a blowdown pipeline; the water distribution tank is connected with the water storage tank through a drainage pipeline; a humidity sensor is arranged at the outer part of the water distribution tank; the water distribution tank is internally provided with a sewage circulation chamber and a clean water circulation chamber; the blowdown tank is internally provided with a dirt discharging chamber, a sewage discharging chamber and a dirt storage chamber. The intelligent informationized drainage system of the building has the beneficial effects that rainwater discharged by the drainage pipeline of the building is reasonably recycled by the system through an automatic control method, so that water resources are saved; meanwhile, the building becomes more intelligent and informationized.