Abstract: With the titanium-bearing blast furnace slag as the main object, the effects of particle size and dose of adsorbent, pH value and initial concentration of solution and adsorbing time on the adsorbing-dephosphorization were investigated experimentally. The results showed that the adsorbility of ultrafine titaniumous blast furnace slag to remove phosphates increases with decreasing particle size and increasing slag's dosage, pH value and reaction time, but decreases with increasing initial concentration of phosphates if slag particle size is greater than 10 μm. The adsorbtion process of phosphates by the slag is so rapid that the saturated adsorbtion is basically available within 20~30 min. The XRD patterns and SEM images before and after the absorbtion of phosphates by the slag were compared with each other, and the results showed that massive crystals form on the slag surface after absorbtion and adhere to powdered surface with the multi-layer adhesion found partially.