The invention discloses a double-row stayed-cable lightning-protection facility mounting trolley and further discloses a mounting method of the double-row stayed-cable lightning-protection facility mounting trolley. The double-row stayed-cable lightning-protection facility mounting trolley is used for conducting travelling operation on double-row stayed cables and comprises a trolley frame, a first connecting frame, a second connecting frame and a driving device. The trolley frame comprises a bottom plate, the first connecting frame is assembled on one side of the trolley frame, and two firstrollers are arranged on the first connecting frame. The second connecting frame is assembled on the other side of the trolley frame, and two second rollers are arranged on the second connecting frame.The driving device is used for driving a trolley to move along the stayed cables, and meanwhile the distance between the first rollers and the bottom plate is larger than that between the second rollers and the bottom plate. The double-row stayed-cable lightning-protection facility mounting trolley and the mounting method thereof are suitable for mounting operation of small-distance large-span double-row stayed-cable lightning-protection facilities of different angles, the construction quality can be ensured, the construction speed is increased, and the safety risk is greatly reduced.