I n CR networks, a transmitting and receiving beamforming algorithm is proposed. I n tran smitting beamforming, a multi beam algorithm is proposed to send different sign als to different secondary users. In receiving beamforming, a low side lobe beamformin g a lgorithm is presented. To avoid the interference when primary and secondary users share the same spectrum, the problem of transmitting beamforming is transf orme d i nt o the one that can be solved by CVX toolbox. In receive beamforming, based on the method of array pattern optimization, a low side lobe level rec e iving beamforming algorithm is proposed in primary base station to suppress the wh ite noise an d unexpected interference. Extensive numerical results using simulated wireless channels in two dimensions are presented to verify the effectiveness of the algo rithm.