<p>In engineering practice, there are many factors causing the vibration to which rods are usually subjected. Generally, the vibration of elastic rods motivated by determined vibration excitations can be controlled effectively. However, the working frequency of vibration excitation may vary due to environmental changes, the working conditions of equipment, and other factors. Consequently, it remains a challenge to restrict the longitudinal vibration of elastic rods within a wide frequency band. In order to meet the relevant engineering requirements and address the existing limitations, the longitudinal vibration control of an elastic rod within a wide frequency band is explored in this study through an adjustable stiffness internal support. To achieve this purpose, the variable stiffness longitudinal vibration control theory of the elastic rod is validated. The model of an adjustable stiffness internal support is designed, constructed, and tested, demonstrating that the stiffness coefficients of the adjustable stiffness internal support can be effectively controlled. Through the adjustable stiffness internal support, the experiment on longitudinal vibration control of the elastic rod is designed and performed. It leads to the conclusion that the adjustable stiffness internal support within the adjustable working region is effective in restricting the longitudinal vibration within a wide frequency band of the elastic rod. Furthermore, the existence of the adjustable working region in the experiment demonstrates the effectiveness of the adjustable stiffness internal support intended for the variable stiffness longitudinal vibration control of an elastic rod. To sum up, this study provides insights into an adjustable stiffness mechanism for applying the theory of variable stiffness longitudinal vibration control on an elastic rod in engineering practice.</p>