The invention provides a steel bar truss reinforcement system and method for a bricked earth-retaining wall on a foundation pit support top ring beam. The system comprises the earth-retaining wall and a plurality of triangular supports, wherein the earth-retaining wall is arranged on the top ring beam, and the triangular supports are supported on the inner side of the top ring beam along the longitudinal direction of the top ring beam at intervals. A plurality of vertical embedded bar pairs connected with the bottoms of the corresponding triangular supports are embedded into the top ring beam, a plurality of horizontal embedded bars connected with the tops of the corresponding triangular supports are embedded to the top of the earth-retaining wall, and all the triangular supports are connected through horizontal fixed steel bars to form a triangular truss, namely a hyper-static truss supporting system. As three angles of each triangular support of the triangular truss are connected with the preliminary embedded bars, the triangular truss is the hyper-static truss supporting system, stability and the mechanical performance of the triangular truss can be ensured, the earth-retaining wall is stably supported, safety of a foundation pit can be ensured, the bearing capacity of the ground outside the foundation pit can be improved, and the system has the advantages of mounting rapidness, efficient and convenient support property and high waste steel bar use ratio.