A method for dynamically adjusting transmit power is disclosed, including: acquiring strength of a signal received by a receiver of a first system; determining whether the acquired strength is less than a sensitivity of the receiver corresponding to strength of a signal currently transmitted by a transmitter, based on correspondence information of strength of signals transmitted by the transmitter and sensitivities of the receiver, and the strength of the currently transmitted signal; if yes, then decreasing the strength of the currently transmitted signal to be equal to or less than the strength of a signal transmitted by the transmitter corresponding to a sensitivity of the receiver being regarded as the strength of the received signal. Corresponding control device and communication system are also provided. The manufacture cost of the device is reduced by the present invention. Meanwhile, better performance can be kept for the receiver.