Abstract: Phenol-containing waste water has become a major issue in the water treatment industry because of its low biodegradability, intractability, and toxicity. Using steel slag as raw material, acid and alkali modified steel slags are obtained by different methods. Scanning electron microscopy（SEM） and specific surface area（BET） test had been taken to analyze the structure, properties and chemical composition of steel slag before and after modification. The osmotic process was applied to the phenol treatment of organic waste water. The reaction time, steel slag particle size, solution pH, and the like were discussed in detail. The effect of slag dosing amount on the removal of phenol in organic wastewater was investigated. The optimal treatment conditions were determined and the kinetics principle was analyzed. The results showed that for unmodified steel slag the optimal treatment parameters are as follows: particle size in 74～150 μm steel slag dosing amounts 8 g/L, the reaction time 55 minand pH=4, the resulted removal rate of phenol in waste water is 41.2%. For acid and alkali-modified slag the removal rate are 36.08% and 38.67% respectively.