<p>The utilization of multi-component environmentally friendly modifiers for wood offers an effective approach to enhancing modification efficiency and improving the overall properties of wood. In this study, a ternary modification system comprising lactic acid, taurine, and boric acid was employed to impregnate poplar wood. The effects of this modification on the physical-mechanical properties, thermal stability, and flame retardancy of the treated wood were systematically evaluated, and the underlying mechanisms were explored. Results revealed that lactic acid underwent polymerization within the wood structure, with substantial polymer accumulation observed in cell lumens. The presence of nitrogen, sulfur, and boron in the modified wood confirmed the successful incorporation of taurine and boric acid. Compared with the control, the treated wood demonstrated reduced water uptake, improved dimensional stability and thermal stability, but decreased mechanical properties. Although boric acid partially mitigated the loss in compressive strength parallel to grain, further optimization is needed to minimize these drawbacks. Flame retardancy was significantly improved, as evidenced by reduced heat release and smoke production, primarily due to the synergistic effects of taurine and boric acid. Overall, this ternary modification presents an eco-friendly and efficient method for enhancing the comprehensive performance of wood.</p>