The invention provides a whole-process control system for a boiler water level. The whole-process control system comprises a magnetic levitation water level device, a differential pressure water level device and a switching device, wherein the magnetic levitation water level device is used for measuring the boiler water level value in a boiler, and outputting the boiler water level valve to a far end; the differential pressure water level device is used for obtaining the boiler water level value in the boiler through hydraulic pressure and outputting the boiler water level value; the switching device is respectively connected with the magnetic levitation water level device and the differential pressure water level device, is used for comparing the boiler water level outputted by the magnetic levitation water level device with that outputted by the differential pressure water level device, and selecting the boiler water level value outputted by the magnetic levitation water level device or a differential pressure water level device as a water level reference according to the comparison result, and is connected with a water level control system. Therefore, not only the labor intensity of workers is reduced, and misoperation risks, caused possibly by a large number of operations, are avoided, but also the absolute starting time of a unit is saved, and the energy consumption is reduced.