The utility model provides a test steel beam for the plane gate of a hydro junction, and relates to the field of water-conservancy and water-power equipment, which structurally comprises a test steel beam (2). The top end of the test steel beam is provided with a lifting handle (4). The lifting handle (4) is provided with a hanging hole (5). The test steel beam (2) is provided with a water flowing hole (3) used for the water to flow through. The two sides of the upstream surface of the test steel beam (2) are provided with four main sliding blocks (1). The two sides of the downstream surface of the test steel beam (2) are provided with four reverse sliding blocks (6). The bottom of the test steel beam (2) is provided with a water leakage hole (7). According to the technical scheme of the utility model, by means of the test steel beam, the flatness of embedded parts in the gate slot and the bottom bank of a plane gate can be tested. Meanwhile, whether foreign matters exist on underwater embedded parts in the bottom bank of the plane gate or not can be detected in advance. In this way, the plane gate is well prepared for being loaded. By means of the test steel beam, not only the flatness of embedded parts in the gate slot and the bottom bank of the plane gate, but also whether foreign matters exist on underwater embedded parts in the bottom bank of the plane gate or not, can be detected in advance. Therefore, the loading and plugging process of the plane gate is ensured to be conducted smoothly. The test steel beam is cost-saving, simple in structure, low in cost, and convenient in detection.