A control circuit for a peripheral component interconnect express (PCI-E) device includes a power detecting unit and a parameter adjustment unit. The power detecting unit is coupled to a wireless communication transmitter, and arranged to detect a spectrum intensity value of an output spectrum of the wireless communication transmitter. The parameter adjustment unit is coupled to the power detecting unit, and arranged to produce at least one control signal according to the spectrum intensity value and adaptively adjust a parameter setting of the PCI-E device in accordance with the at least one control signal.