Immobilized cellulase was pretreated by ultrasound. Based on the single factor and response surface methodology, the effects of ultrasonic parameters, such as ultrasonic time, ultrasonic frequency and ultrasonic power, as well as enzymolytic temperature and pH value of CMC-Na buffer solution after pretreated were investigated. A mathematical model was established and analyzed to describe the relationships between the studied factors and enzyme activity. The optimum treatment parameters were as follows: enzymolytic temperature of 58.73℃, pH value of CMC-Na buffer solution of 3.0, ultrasonic time of 16.88min, ultrasonic frequency of 22.33kHz and ultrasonic power of 26.77W. Under the optimum conditions, enzyme activity of immobilized cellulose increased by 9.75%.