The invention relates to a frequency adjustable vibration damping device for a low-frequency line spectrum of vibratory equipment and a vibration damping method thereof. The frequency adjustable vibration damping device comprises a dynamic vibration absorption system formed by a cantilever rod and a particle damper. The frequency adjustable vibration damping device is simple in structure and convenient to use; and the dynamic vibration absorption system formed by a cantilever rod and the particle damper can accurately control the low-frequency vibration line spectrum of the vibratory equipment, has relatively strong applicability and is suitable for the vibration suppression of various equipment in different directions. The frequency adjustable vibration damping device has very good nonlinear low frequency damping performance and the characteristics that the larger the vibration amplitude is, the better the damping effect is. When the dynamic vibration absorption system resonates withthe equipment, the dynamic vibration absorption system has relatively large vibration amplitude, can fully utilize the dissipation mechanism of particle damping, effectively dissipates the low-frequency vibration energy, and reduces the low-frequency line spectrum vibration of the vibratory equipment.