The discharge door hydraulic drive system of internal mixer was designed.The simulation model was established based on AMESim and the dynamic performance was simulated.The influences of accumulator pressure and volume on opening time of discharge door were analyzed.The simulation results show that the designed hydraulic drive system can open the discharging gate of internal mixer in a very short time;when the accumulator pressure increases or the accumulator bladder volume increases,the opening time of the discharging door reduces.