A signal processing method, an apparatus and a non-transitory computer readable storage medium are provided. A plurality of segment signals are taken out based on a time series from a physiological signal, and each segment signal is determined as a desirable signal or an undesirable signal. In response to the ith segment signal is determined as the undesirable signal, under the condition of determining that both of the (i−2)th segment signal and the (i+2)th segment signal are the desirable signals, the ith segment signal is reserved. A plurality of instant heart rates are calculated based on the desirable signals and the reserved undesirable signals.