The current experiment was carried out to investigate effects of combinations of Lactobasillus buchneri (LAB), Aspergillus niger (AN), Candida tropicalis (CT), Bacillus subtilis (BS) and Lactobacillus plantarum (LAP) on quality of cassava residue, and to find the best strains combination. In this study,cassava residue were used for fermentative raw material, LAB, AN, CT, BS and LAP were combined in accordance with different strains by 1: 1, there were five different combinations in this experiment. Combination 1: LAB+AN+CT+LAP;combination 2: LAB+AN+BS+LAP;combination 3: LAB+CT+BS+LAP; combination 4: AN+CT+BS+LAP; combination 5: LAB+AN+CT+BS+LAP;1% urea or 1% urea+0.6% brown sugar was added to each combination, the blank group was not added any additives, 1% urea was added to the control group Ⅰ, 1% urea+0.6% brown sugar was added to the control group Ⅱ, water content in each group was about 65% by modulating with physiological saline, each group was fermented in the vacuum of polyethylene film bag for 10 days. The results showed as follows: 1) the effects of different microbial inoculants on the nutrition composition of cassava residue, the result showed the combination of LAB+AN+CT+BS+LAP+urea+brown sugar was superior to the four strains combination. The combination 5 get the best quality improvement of cassava residue, compared with the blank group, the pH was significantly reduced (P<0.05), the acetic acid and propionic acid contents were significantly improved (P<0.05), the neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents were the lowest, and significantly lower than those in blank group and control groups (P<0.05), the crude protein content was the highest, and significantly higher than those in blank group and control groups (P<0.05). 2) It was favorable to propionic acid production by adding the corresponding strains+urea+brown sugar to the cassava residue fermented by the mixed strains. 3) When the urea was added into the fermentation medium, the crude protein content in cassava residue was significantly increased (P<0.05). 4) Urea and brown sugar were added into cassava residue for improving the nutrition composition during the fermentation process of cassava residue which was better than that only urea was added into cassava residue. In conclusion, solid-state fermentation using LAB, AN, CT, BS, LAP, urea and brown sugar can offer an effective alternative to improve the quality of cassava residue.