In order to detect the presence of primary users, spectrum sensing is considered as one of the most important and basic functions of cognitive radio. The purposes of spectrum sensing areis to detect primary user, secondary users, and white space (nobody using). In this paper, we go on to investigate the effect of channel gain and signal-to-noise ratio (SNR), oin the cooperation between secondary users in weighted, combining energy detection to improve the probability of detection to raise the receiver operating characteristics (ROC) curve. Moreover, the optimal linear combining weights at the fusion center hasve been derived to calculate the optimal transmit power for each node, for maximizing the detection probability. Thusly, cognitive users node can designate its own particular transmit power by exchanging information with its own neighbours. The simulation results show that the ROC curve of the secondary users is raised, apparently, and our results can be increasing the detection probability for various numbers of cognitive radio users under a low number of samples.