The present invention provides a reinforcing structure and method for reinforcing valve towers, mainly aiming at valve towers with three or more layers, wherein the four corners of the side face of each layer of a valve section of the valve tower are provided with connecting flanges, and connecting rods are used for connecting the corresponding connecting flanges of adjacent valve towers of the same bridge arm to realize lateral reinforcing. The connection modes of lateral reinforcing mainly include horizontal connection, interleaving connection and cross-layer connection. The invention provides various reinforcing solutions for flexible DC valve towers in the environment of long-term turbulence and strong vibrations, the reinforcing structure is simple and effective, high in reliability and operability, and easy to disassemble, and the stability and safety of the valve towers during transportation and operation are enhanced.