Peniceillium brasilianum KUEB15 was utilized for cellulase production and medium optimization was investigated. The optimal compositions of the variables for maximum CMCase production by central composite rotatable design were 12.39 g/L of corn stover, 0.48 g/L of urea and 6.12 g/L of ammonium sulfate. The predicted CMCase activity by the model was 1.207 Unit/ml, and the observed CMCase activity which was produced in optimal media was 1.180 Unit/ml. The activity of CMCase from P. brasilianum KUEB15, which was fermented in optimal media by RSM, was found to be 1.61 fold increased than that in the Mandel's medium (0.731 Unit/ml).