In this study, a statistical model which can be used to describe rate of reduction of chemical oxygen demand ( COD) in anaerobic digestion of hen manure was developed. Temperature, pH, and total solid percent were chosen as a 2(3)-factorial experimental design and the effects of these factors on the rate of reduction of COD were examined in batch reactors according to the Box-Wilson experimental design method. Experimental results were evaluated statistically by using "Design Expert 7.0.3 Trial" package program. All reactors were inoculated with equal volume of anaerobic digester sludge. With the use of the developed model maximum rate of reduction of COD was obtained as 368,17 mg COD/L.g solid. day when temperature, pH and total solid percent were 35 degrees C, 6.9, 7.01 (g/100 g) respectively.