The present invention discloses a method and device for suppressing vibration of boom of concrete pump truck, in which the boom cylinder is connected with the vibration suppression cylinder; the information about hydraulic pressure in the boom cylinder and/or about changing of concrete pumping direction is monitored by a pressure sensing unit in real time; the monitored information about hydraulic pressure and/or about changing of concrete pumping direction is transmitted to the control unit for vibration suppression cylinder; the control unit for vibration suppression cylinder analyzes and processes the monitored information and adjusts the volumes of the rod side chamber and the non-rod side chamber in the vibration suppression cylinder such that the vibration suppression cylinder may generate a pulsed vibration and the pulsed vibration at the end of the boom is less than or equal to the vibration amplitude caused by the intermittent concrete supply at the end of the boom in amplitude, with a phase difference of 180° between the two vibrations. The vibration suppression method and device for boom of concrete pump truck according to the present invention may be simply configured, easily implemented and operated to effectively suppress the boom vibration.