The effects of maltodextrin concentration on the saccharification were investigated by using glucose concentration and yield as the indexes,and the related mechanism was analyzed. The results showed that the glucose concentration and yield of saccharification reaction both increased first and then decreased with the rising maltodextrin concentration. The glucose concentration in the saccharification solution reached the peak( 531. 3 mg/mL) after reacting for 48 h while the initial maltodextrin concentration was 50%. The glucose yield was higher at 20% ~ 40% maltodextrin concentration,reaching 90% after saccharification for 48 h. The glucose yield was lower at 50% maltodextrin concentration at the early stage of the reaction,however it reached 88. 7% after saccharification for 48h and decreased significantly to 69. 3% while the initial maltodextrin concentration reached 60%. The main reasons might be that the molecular density of the maltodextrin increased with the rising concentration in the low concentration solution of maltodextrin. Thus,the probability of collision of enzyme and substrate increased with the rising concentration, which resulted in the increase of glucose concentration and yield. However,as the further rising of the maltodextrin concentration,especially exceeded 50%,the viscosity of the system increased obviously,the water activity of the system reduced,the mobility of water became poor and the free water became less,which might inhibited the saccharification and resulted in decreasing glucose concentration and yield.