A portable computer and an operating method thereof are provided. The portable computer comprises an input device, a power button, a non-volatile memory, a central processing unit (CPU), an embedded controller (EC), and a chipset. The input device inputs a user password, and the non-volatile memory stores a default password. The EC, in a soft off status, determines whether the power button protection item is enabled. The EC locks the power button if the power button protection item is enabled. The EC determines whether the user password is the same as the default password. The EC unlocks the power button if the user password is the same as the default password. The chipset is coupled to the non-volatile memory, the CPU and the EC.