Four-season celery (Petroselinum crispum)is one of high value nutrient and healthy vegetables, with rich nutrition, strong perfume and health care value and is high quality raw material for vegetable juice processing. but low yield of celery juice was one of the main technical bottlenecks restricting the vegetable juice processing. The effects of cellulase adding quantity, enzyme hydrolysis time and enzyme hydrolysis temperature on celery juice yield were studied separately, and response surface analysis was optimized by Box-Behnken design, and interaction of single factor on celery juice yield was analyzed. The regression equation prediction model was established in the paper. The optimum conditions for the application of cellulase in celery juice were as follows:cellulase addition quantity 0.06%, enzymatic hydrolysis time 1.56 h, enzymatic hydrolysis temperature 40.14℃, and the yield of celery juice was 78.38%. The actual yield of celery juice (78.72%±0.25%) was better fitting of the predictive value.