The invention provides concrete pumping equipment and an arm-support-vibration semi-active control device and an arm-support-vibration semi-active control method thereof. The arm-support-vibration semi-active control device comprises a plurality of sections of arm supports (10) and extension mechanisms (20) connected between two adjacent sections of arm supports (10). The arm-support-vibration semi-active control device further comprises changing dampers arranged at the extension ends or fixed ends of the extension mechanisms (20) in series connection mode, sensors arranged on the arm supports (10) and controllers (40) connected with the sensors. Signal output ends of the controllers (40) are connected with the changing dampers to control damping force of the changing dampers, and the changing dampers exert damping force in the reversed direction with the vibration direction of the arm supports (10) on the arm supports (10). The arm-support-vibration semi-active control device can not only passively play the roles of damping, energy consumption and vibration reduction, but also actively play the roles of vibration control, thereby being good in control effect on arm support vibration, simple in structure and flexible and convenient to use.