Provided are a roof truss node buckle plate and a lightweight steel structure thereof. A plate body of the roof truss node buckle plate is formed by stamping metal thin-wall plates and comprises chord member connecting plates and a plate-shaped integrated connecting piece of a web member connecting plate. The plate body is provided with a stamping press rib which protrudes towards the front of the metal thin-wall plates and does not pass through the edge of the plate body. The stamping press rib is composed of a horizontal stamping press rib, a left vertical stamping press rib, a right vertical stamping press rib, an upper arc-shaped stamping press rib and a lower arc-shaped stamping press rib. The horizontal stamping press rib is arranged on the chord member connecting plates, the left vertical stamping press rib is distributed from the chord member connecting plates to the web member connecting plate, and the right vertical stamping press rib is distributed from the chord member connecting plates to the web member connecting plate. The roof truss node buckle plate greatly improves bearing capacity and rigidity of the connecting plates and enables the connecting plates to be firmer, and the connecting plates cannot be bent or deformed easily when particularly subjected to force in a plurality of directions.