Abstract: In order to study the experimental conditions of 3,5- Dinitrosalicylic acid( DNS) to measure the activity of carboxymethyl cellulase( CMCase),factors including wavelength,enzymatic reaction temperature and time,p H,solvent amount of crude enzyme and substrate,substrate concentration,coloration time and blank experiment were used by a single factor test to explore the influence on the results of CMCase activity.A relatively optimal solution which was applicable to CMCase activity was established by using the method of response surface analysis( RSA)and variance analysis.Results showed that the best conditions for detecting the activity of CMCase was at 520 nm wavelength,45℃ and 30 min for enzymatic reaction,p H7.0,substrate concentration 12 g / L,coloration 15 min.