The invention provides a cloud treatment steam boiler blowdown system with the blowdown time capable of being intelligently adjusted. A boiler carries out regular blowdown; a central diagnostic monitor automatically sets the blowdown time according to a ratio of the mass of steam to the mass of water input the boiler; the central diagnostic monitor is in data connection with a cloud server so as to transmit monitored data to the cloud server; the cloud server is connected with a client; and the client can obtain the monitored data through the cloud server. By monitoring the water input amountand the steam generation amount quantity of each boiler in real time, the blowdown time is automatically adjusted, the client can timely know operating conditions of the cloud treatment steam boiler blowdown system, adjustment on blowdown parameters can be carried out through the client timely, and abundant heat energy waste arising from a failure of the cloud treatment steam boiler blowdown system is prevented.