Abstract: To determine the optimum carbon source and dosage to for form the bio-floc formation in Penaeus monodon culture systems, we added three kinds of carbon source including glucose, sucrose and molassesin the culture system at C/N ratio of 20:1.The sucrose was added into the culture systems at daily feeding ratios of 0%, 25%, 50%, 75% and 100%. Results from present study indicate show that all carbon sources tested in the present study could significantlyincrease the special growth rate (SGR) of P. monodon （P0.05). Sucrose can could significantly increase the survival rate (SR) of P. monodon (P0.05). Comparedwith the other groups, 75% of sucrose can could significantly improve the SGR and SR of P. monodon in the second experiment (P0.05), and sucrose canould promote heterotrophic bacteria and phytoplankton reproduction, and indirectly reduce concentration of harmful substances in water such as NH4-N and NO2-N, but adding excessive sucrose will would be counterproductive. The results showed reveal that adding 75% of sucrose added iwas the most suitable condition for bio-floc formation in P. monodon culture systems, and which could promote the growth ofP. monodon.