A signal detection method associated with a constellation diagram corresponding to a modulation scheme is provided for enhancing the reliability of code rate search. A mask is provided between two adjacent constellation points in the modulation scheme. The signal detection method includes: receiving a plurality of signals, and mapping the plurality of signals to the constellation diagram; when a first signal among the plurality of signals is located in the mask, discarding the first signal; and when a second signal among the plurality of signals outside located in the mask, determining a constellation point corresponding to the second signal.