A signal detection method applied in an electronic device includes: resetting each optical sensor at a first time point; collecting a first signal output by the optical sensor at the first time point, a second signal output by the optical sensor at a second time point, a third signal output by the optical sensor at a third time point, and a fourth signal output by the optical sensor at a fourth time point; obtaining a first difference value between the first signal and the second signal and a second difference value between the third signal and the fourth signal, and determining a sum of the first difference value and the second difference value as a signal variation amount in a current cycle. Also disclosed are an associated electronic device and a non-transitory computer readable storage medium.