The invention discloses a vibration amplitude adjustable device used for precise vibrational picking of medlars. The device comprises a support, a rotary driving motor fixed on a horizontal support surface of the support and a vibration amplitude adjustable mechanism connected to the rotary driving motor. The vibration amplitude adjustable mechanism comprises a telescopic rod, a horizontal reciprocating rod, a gripper and a limiting block. The limiting block is fixed on the horizontal support surface of the support. Horizontal limiting holes are arranged in the limiting block. The horizontal reciprocating rod penetrates through the horizontal limiting holes to perform horizontal limiting operation. The bottom end of the telescopic rod is fixedly connected with an output shaft of the rotarydriving motor. The top end of the telescopic rod is hinged onto the inner end of a horizontal reciprocating rod. The outer end of the horizontal reciprocating rod is equipped with the gripper. Compared with the prior art, the vibration amplitude of different varieties and ages of medlars can be changed on a large scale so that precise vibrational picking of medlars is realized. Additionally, thevibration amplitude adjustable device is simple in structure and capable of adjusting the vibration amplitude at will. The vibration amplitude adjustable device has advantages of reduction in medlar breakage rate and labor cost.