A signal receiving apparatus, applicable in a wireless system calibrating direct current offset, includes: an adjusting circuit arranged to receive an receiving signal having a first DC (Direct Current) signal, and adjust the first DC signal to generate the receiving signal having a second DC signal according to an adjusting signal; a first arithmetic circuit arranged to generate an error signal according to the second DC signal and a target DC signal; and a second arithmetic circuit arranged to calculate an error signal slope according to the error signal, and update the adjusting signal according to the error signal slope and the error signal.