A signal detection circuit is used for detecting signal squelch of a differential input signal to generate a corresponding digital output signal. The signal detection circuit includes: a reference voltage generator for generating a reference voltage of which the common mode voltage tracks the common mode voltage of the input signal; a real-time signal judgment circuit, real-time rectifying and amplifying a difference between the input signal and the reference voltage; and a deglitch circuit, sampling and/or amplifying an output signal of the real-time signal judgment circuit, and transforming sampling results into the digital output signal to reflect signal squelch of the differential input signal.