The inner hole machining of long axis parts has always been a difficult problem in the field of mechanical cutting, and the quality of the inner hole directly determines the performance of the parts. The inner hole of the workpiece is usually processed using a large diameter boring bar. Due to the large length-to-diameter ratio of the boring bar, the overall stiffness will be greatly reduced, and the boring bar will produce vibration. The vibration of the boring bar directly affects the surface quality of the workpiece, and in severe cases, it can lead to the workpiece being scrapped. Therefore, researching vibration damping boring bars that reduce vibrations in deep hole machining is of significant importance. A new type of boring bar with variable damping dynamic damper has been designed, and its basic parameters have been calculated. Based on a two degree of freedom dynamic model, the vibration reduction characteristics of a boring bar were analyzed, and the variation patterns of boring bar vibration under different damping ratios and excitation frequencies were obtained. A simple and reliable variable damping vibration reduction method has been proposed, which can achieve the best vibration reduction performance by adjusting the damping size.