The effect of masss of natural diatomite, initial dye concentrations, pH and temperature on adsorption was investigated. The adsorption of reactive dye was slightly increased then decreased with rising amouts of natural diatomite that is increasing competition of natural diatomite. The removal rate of reactive black increase with the temperature because of endothermic reaction. The removal rates of reactive black from solution were decreased as the pH increase and gain the maximum in low pH. The removal rate for all concentrations were rapid at initial stages and then keep increase gradually until the progress until equilibrium reached.