Abstract: With milk protein peptide beverage as the raw material , through the screening of three indexes including bitter value, TCA-SNI and total protease activity, the composite bacteria with lower bitter value, higher total protease activity, higher TCA -SNI was obtained. Results showed that, effect of debittering order was composite bacteria>yeast>lactobacillus, the optimal addition of composite bacteria was 1% , fermentation time was 7h, total protease activity reached 32U/mL, TCA-SNI reached 34.5%, bitter value reached 0.5.