The invention relates to an expansion water kettle with a liquid level alarming function. The expansion water kettle includes an expansion water kettle body, a signal input unit and a signal processing unit. The expansion water kettle body is provided with an alarming liquid surface line; the signal input unit is used for providing different voltage input signals for the liquid level signal processing unit according to the liquid level in the expansion water kettle body; and the signal processing unit is electrically connected with the signal input unit and is used for judging whether receivedvoltage values in a certain period are all larger than a preset voltage threshold value or not, and alarming signal sending is controlled by the signal processing unit according to judging results. According to the expansion water kettle with the liquid level alarming function, monitoring of workers on the liquid level of the expansion water kettle body can be reduced, thus consumption of workertime and worker energy is lowered, and probability of occurrence on a cooling system is reduced.