High water content and rich organic matter are the most obvious characteristics of water plant tailings. Solidification is one of the best methods for treating tailings of water plants. It can not only improve the mechanical properties of soil, but also reduce the dissolution of heavy metal pollution ions. The traditional solidifying agent cement lime and industrial waste by-product gypsum are used as the main solidifying materials to solidify the tailings of the water plant, and the engineering performance of the tailings is improved, so that the solidified tailings of the water plant can be used as roadbed backfill soil. According to the unconfined compressive strength, water resistance, freeze-thaw resistance, swelling ratio, and leachate of the hardened body, its road performance was determined. The microstructure and hydration products of the cured tailings were analyzed by X-ray diffraction and scanning electron microscope. The experimental results show that 4% cement + 6% lime and 16% by-product gypsum can meet the requirements of solidified water plant tailings as roadbed filling. Adding strong oxidants to decompose organic matter can improve the curing effect of the curing agent.