A signal transmitting circuit includes: a signal generating circuit arranged to generate an output signal to a loading device according to an input signal; an adjusting circuit; and a matching circuit having a first port coupled to the adjusting circuit and a second port coupled to the signal generating circuit, wherein the second port is arranged to couple to the loading device so as to provide a matching impedance corresponding to the loading device; and the adjusting circuit is arranged to generate an adjusting signal of which a voltage applied on the first port is substantially equal to a voltage of the output signal applied on the second port.