A level shifter device and an operation method thereof are provided. The level shifter device includes a buffer, a first level shifter and a dynamic voltage regulation circuit. The buffer includes an output terminal. The first level shifter has a first input terminal coupled to the output terminal of the buffer. The first level shifter has a reference voltage terminal coupled to an analog reference voltage. The dynamic voltage regulation circuit generates a dynamic voltage having a level varied according to a bounce of the analog reference voltage, and provides the dynamic voltage to at least one of the buffer as a power supply and the first level shifter as a bias voltage.