An overheat protection controller assembly of a liquid heating vessel, comprising: a control body; a monolithic conjoined double-actuating thermal sensitive bimetal actuator arranged on the upper surface of the control body, the monolithic conjoined double-actuating thermal sensitive bimetal actuator comprises two conjoined actuating units which are formed of a single piece of the same bimetal sheet, each of the two actuating units which are adjacent to each other and conjoined has a closed outline perimeter of the actuating unit, the bimetal sheet enclosed by each said actuating unit's outline perimeter forms an actuating unit which has an independent function of overheat actuation, each said actuating unit's outline perimeter intersects with the other actuating unit's outline perimeter, the monolithic conjoined double-actuating thermal sensitive bimetal actuator has a common join part which is located at the intersection part of said two actuating units' outline perimeters and effectively makes the two actuating units form the monolithic conjoined double-actuating thermal sensitive bimetal actuator, the monolithic conjoined double-actuating thermal sensitive bimetal actuator is mounted on the control body via a central mount point of each said actuating unit, the periphery of each said actuating unit is configured to be able to kick downwards to produce an actuation movement on an overheat condition; and two groups of switch contacts arranged on the control body correspondingly, wherein each group of the switch contacts cooperates with the periphery of a corresponding actuating unit, wherein the actuating units are such configured that a downward actuation movement of the periphery of any of the actuating units will open a corresponding group of the switch contacts and cut off the power supply of the heater of the liquid heating vessel. a control body; a monolithic conjoined double-actuating thermal sensitive bimetal actuator arranged on the upper surface of the control body, the monolithic conjoined double-actuating thermal sensitive bimetal actuator comprises two conjoined actuating units which are formed of a single piece of the same bimetal sheet, each of the two actuating units which are adjacent to each other and conjoined has a closed outline perimeter of the actuating unit, the bimetal sheet enclosed by each said actuating unit's outline perimeter forms an actuating unit which has an independent function of overheat actuation, each said actuating unit's outline perimeter intersects with the other actuating unit's outline perimeter, the monolithic conjoined double-actuating thermal sensitive bimetal actuator has a common join part which is located at the intersection part of said two actuating units' outline perimeters and effectively makes the two actuating units form the monolithic conjoined double-actuating thermal sensitive bimetal actuator, the monolithic conjoined double-actuating thermal sensitive bimetal actuator is mounted on the control body via a central mount point of each said actuating unit, the periphery of each said actuating unit is configured to be able to kick downwards to produce an actuation movement on an overheat condition; and two groups of switch contacts arranged on the control body correspondingly, wherein each group of the switch contacts cooperates with the periphery of a corresponding actuating unit, wherein the actuating units are such configured that a downward actuation movement of the periphery of any of the actuating units will open a corresponding group of the switch contacts and cut off the power supply of the heater of the liquid heating vessel.