The invention discloses a demodulation method in molecular communication. The demodulation method is characterized by comprising the following steps: assuming that an originating party adopts a time-slot on-off keying (OOK) method to represent a digital signal, judging whether a molecular concentration received in a time slot has an obvious rising process or not during the demodulation process, if the molecular concentration has the obvious rising process, demodulating the molecular concentration to be information bit '1', and otherwise demodulating to be information bit '0'. By adopting the demodulation method, the defect of unreliability caused by demodulation by virtue of detection of the molecular concentration can be overcome; and moreover, the molecular concentration only needs to be sampled in a period of time after the beginning of each time slot rather than in the whole time slot, so that the calculation burden of the demodulation algorithm is alleviated. Meanwhile, the technical scheme is realized according to a variation rate of the molecular concentration, so that the influence of the intersymbol interference caused by a molecular aggregation problem on a demodulation result can be effectively alleviated, the reliability of the demodulation algorithm is improved, and the demodulation method is generally suitable for demodulating information in the molecular communication based on a diffusion way.