The embodiment of the invention provides a beam forming method of a wireless communication system and a baseband processing unit. The method comprises the steps of obtaining a first channel state wheneach radio frequency antenna transmits data to each terminal; according to the first channel state and the first beam forming factor of the radio frequency antenna, obtaining an optimization objective function of total time delay of required data obtained by all terminals under the constraint condition; wherein the constraint condition is that the first transmission power of any radio frequency antenna during data transmission is less than a preset first power threshold, and the first transmission rate of any terminal for receiving data from all radio frequency antennas is greater than a preset first rate threshold; according to an optimization objective function of the total time delay, all optimized first beam forming factors are obtained by constructing the optimization objective function of the total time delay and then adopting the weighted least mean square error estimation algorithm, and the optimized first beam forming factor of each radio frequency antenna when the total timecalculation is minimum is obtained.