An integrated circuit and an operation method thereof are provided. The integrated circuit includes a voltage detecting unit, a central processing unit, a memory unit and a control unit. The voltage detecting unit detects a system voltage and correspondingly outputs a voltage state signal. The central processing unit has at least one register. When the system voltage is downed to a voltage level lower than or equal to a brown-out voltage and greater than a reset low voltage, the control unit stores values of the registers into the memory unit.