The invention discloses a complex enzyme preparation for efficiently preparing a mannose oligomer. The complex enzyme preparation comprises 100-1000 IU/mL of beta-mannose and 50-2000 IU/mL of cellulose based on the total weight of the complex enzyme preparation, and further comprises peptones, starch, potassium sorbate and xylitol, wherein the cellulose is beta-endoglucanase. The invention further provides a method for preparing the mannose oligomer by the complex enzyme preparation. The method comprises the following steps: mixing konjac fine powder, water and the complex enzyme preparation till the concentration of the konjac fine powder is 5-40 g/L, wherein through adjusting the adding quantity of the complex enzyme preparation, a condition that 10-80 IU of beta-mannose exists in each gram of the konjac fine powder in a corresponding manner is ensured; after mixing, carrying out enzymolysis at 20-70 DEG C for 1-10 h. The catalyst efficiency of the complex enzyme preparation is higher than that of single enzyme. The preparation further comprises other components besides the enzymes, the components are combined with the two enzymes, the enzyme activity residual rate is high, the catalytic efficiency is higher, and the catalyst is more stable.