The present invention provides a method, a device, and a system for processing a communications system signal. The method includes: acquiring, by a communications system of a first standard, a first message, where the first message carries a signal strength, sent by a communications system of a second standard, on a frequency where interference of the communications system of the second standard on the communications system of the first standard exists; and performing, by the communications system of the first standard, according to the signal strength, filtering processing for a signal to be processed of the communications system of the first standard. In embodiments of the present invention, interference can be reduced and receiving performance can be improved.