Primary user (PU),In order to improve sensing perfo rmance of traditional energy detection under low signal-to-noise ratio (SNR),a new method is proposed,in which cognitive user automatically adjusts the detection threshold based on changes in the radio environment.Fusio n center applies coordinate search algorithm to provide optimal control parameter for the cognitive user.Based on center threshold,cognitive user dynamic sets the detection threshold according to the optimal parameter and ener gy collected by itself,and learns the optimal threshold for specific radio environment by exchanging information w ith the fusion center.In addition, differences in sensing contribution of cognitive users are fully considered and a new weighting calculation method is designed to reflect the differences.Experimental results sho w that the proposed spectrum sensing method has excellent robustness to nois e fluctuation,and can improve detection probability and reduce error probability simultaneously.The detection probability is as high as 96.9% while SNR is －20dB,which is much higher than those of o ther methods.