The invention relates to a joint spectrum sensing method based on decision threshold optimization. The method comprises the following steps: cognitive radio network models sensed by multi-user joint spectrums are established in sequence, cognitive users receive signals sent by authorized users, after the cognitive users obtain an optimal threshold of energy detection decision, the cognitive users respectively carry out adaptive local energy detection on the spectrums of the authorized users, then a spectrum sensing fusion center selects an optimal cooperation cognitive user participating in cooperation according to an adaptive fusion judgment criterion, in accordance with the spectrum detection results of the cognitive users and the signal to noise ratios per se, in order to improve the detection probability while reducing the fusion calculation quantity; and a global detection probability after weight OR criterion cooperation is used as a joint spectrum sensing result according to the detection probability of the selected optimal cooperation cognitive user. The joint spectrum sensing method can be adaptively adjusted and used for obtaining the optimal decision threshold of energy detection decision and accurately determining the optimal cooperation cognitive user and reducing the fusion calculation quantity of the spectrum sensing fusion center.