The invention discloses a boiler water level control device and a control method thereof. A water inlet pipe and a water outlet pipe are arranged on a boiler. The control device comprises a shell, a single chip microcomputer, a storer, an alarm device, a display, a temperature sensor and a water level sensor, wherein the single chip microcomputer and the storer are arranged inside the shell, the alarm device and the display are arranged on the shell, and the temperature sensor and the water level sensor are arranged inside the boiler. The water level sensor comprises an inductive coil, a silicon steel rod capable of moving up and down in the inductive coil, a floater arranged at the lower end of the silicon steel rod and a guide cylinder used for containing the lower portion of the silicon steel rod and the floater. The lower end of the guide cylinder is provided with an opening with the diameter smaller than the diameter of the floater. Both the inductive coil and the guide cylinder are fixedly connected with the boiler. The boiler water level control device and the control method thereof have the characteristics of being high in detection accuracy, good in stability and reliability, wide in applicable range and not limited by the number of turns and wire diameter of the inductive coil.