The utility model discloses an ultrathin-wall steel structure roof truss bottom corner connector and a connection structure thereof; two side plates of the connector are parallel right-angled trapezoidal side plates and an upper bottom plate is a hollow hexahedron with an inclined plane; the two right-angled trapezoidal side plates of the connector have hollow structures; and an inclined tightening groove and a flat tightening groove are respectively arranged at the upper and lower parts of the two right-angled trapezoidal side plates. In the utility model, the inclined tightening groove and the flat tightening groove are respectively arranged on the upper and lower surfaces of the connector; and the tightening grooves are fixed with upper and lower chords through tightening steel strips. By means of the connection in such manner, the operation is simple, convenient and rapid, the strength is high, the axial constraint performance is favorable, the node integrity is strong, the local bending of ends due to the stress of thin-wall steel is effectively controlled and the bearing capacity of components is improved. The ultrathin-wall steel structure roof truss bottom corner connector is simple in structure, easy for manufacture and construction and strong in applicability. By using combined structures of the connector, the installation and fixation manners are simple, the production and the installation are rapid, the construction period is shortened and the cost is reduced.