Silicomanganese slag (SS) is a byproduct of the ferroalloy industry and cause environmental pollution and consume resources. In this study, the authors explored the use of water glass immersion to improve the performance of SS and used it to produce ultra-high performance concrete (UHPC). The results showed that SS treating with a 2% water glass concentration for 24 hours resulted 16 MPa higher compressive strength for composite than pure UHPC. Additionally, the treated composite had approximately half the mass and compressive strength losses of pure UHPC after freeze-thaw test, indicating that the treatment had a significant positive effect on the freeze-thaw resistance of ultra-high silicomanganese slag performance concrete (UHPSSC). Micro-structural analysis also showed that water glass immersion optimized the morphology of UHPSSC, contributing to improved mechanical performance and freeze-thaw resistance of the composite.