Removing cationic dyes from complex wastewater is significant in industrial wastewater treatment. In this study, we successfully developed a novel magnetic adsorbent, Fe₃O₄@Ti-SiO₂ (FTS), a Ti-doped modified silicon-based material-coated magnetic nanoparticle. This adsorbent demonstrated enhanced selective adsorption capabilities for cationic dyes in complex wastewater under the synergistic interaction of Fe₃O₄ nanoparticles. The FTS composite exhibits superior specific surface area, pore volume, thermal stability, and surface charges, resulting in an ultra-efficient adsorption capacity to methylene blue (MB) (Q_max = 336.74 mg/g), which is 1.56 times higher than that of Ti-SiO₂, 6.7 times higher than that of mesoporous silica particles, and superior to most of the reported silica nanocomposites. In addition, the mixed dye system, high ionic strength solution, and simulated wastewater column adsorption experiments showed that the adsorbent had excellent cationic selectivity, salt resistance, and practical application prospects. This condition is attributed to hydrogen bonding and electrostatic interactions between FTS and cationic dyes, which TGA, VSM, and XPS demonstrated. Moreover, after ten adsorption cycles, the magnetic material may be effectively recycled while maintaining over 97 % of its dye adsorption capability. In conclusion, FTS demonstrates excellent potential as a candidate for the selective adsorption and separation of cationic dyes from complex wastewater.