To study the velocity distribution rule, the sludge deposition and the energy-optimized distribution of the oxidation ditch, the experiment was processed in a WWTP with A/A/O Oxidation Ditch technology. The study individually focused on the velocity distribution of curved sections in out-ditch by testing three operation conditions of the Oxidation Ditch. The result shows: firstly, the velocity of the first ditch is too large; easily lead to waste of energy, intermittent on/off submerged flow drivers can optimize the energy distribution of the system. Secondly, in the second ditch, the flow pattern in crook ditches were very complex, there existed high velocity outside and low inside. For such situation, it is easy to cause sludge deposit in the inside of the ditch. Finally, in order to improve the problem of sludge deposition, the measures were put forward as follows: installing off-center training in curved sections of the second ditch, adjusting the position of submerged flow driver.