Abstract: The activated carbon from sewage sludge was modified with sulphuric acid. The influence of modification time and the concentration of sulphuric acid on adsorption capacity were investigated in the test. In the best condition of modified,the effects of various experimental parameters such as agitation time,initial ion concentration and pH were also studied. The isothermal adsorption characteristics and kinetic dynamics models of original and modified sludge activated carbon adsorbing Cr⁶⁺ were used to analyze the dynamic process.Resultsshow that the sludge activated carbon modified 2 hours with 1 ∶ 5 concentration of the sulphuric acid has the best adsorption capacity,which reaches 9.44 mg/g,increased by 53% compared with the original sludge activated carbon. Adsorption data agrees well with the Langmuir and pseudo-second order kinetic model.