A method for maximizing a battery life and a temperature monitoring device are provided. The method includes detecting whether a low temperature mode is set in the temperature monitoring device; when the low temperature mode is detected, implementing a plurality of measures to enhance the battery life of the temperature monitoring device. The temperature monitoring device includes a memory, a button coupled with a light emitting diode unit, a battery and a processor. The temperature monitoring device is able to implement the method for maximizing life of the battery.