Abstract: Based on the principles of instantaneous optimal active control,it is developed an optimal active control algorithm commanding the structure displacement,velocity and acceleration simultaneously. Moreover,a sem-i active control of the pulsating wind vibration response of multifunctional vibration-absorption of a megaframe structure has been practised by means of magnetorheological damper. The result seems to indicate that the sem-i active control employing magnetohydrodynamic damper may be able to significantly reduce the vibration acceleration response of the main and the secondary frame. Besides, the vibration displacement response of the main frames can also be effectively suppressed. In addition,the control effect of sem-i active control may be superior to that of passive control.