For the development of oil reservoir with bottom water, it is significant to analyze the impact of drawdown pressures on post water breakthrough performance of horizontal wells. Based on a small-scale and discretized physical simulation system, the impact of different drawdown pressures and the influence of changing drawdown pressures in different water cut stage have been discussed. The results show that for thin oil with relatively high viscosity (87.8 mPa.s), keeping a relatively large drawdown pressure in medium and low water cut stage is reasonable. But enlarging drawdown pressure in high water cut stage is harmful to increase ultimate oil recovery. For oil with further lower viscosity (21.4 mPa.s), adopting a small drawdown pressure and increasing it in medium and high water cut stage is reasonable. For the heavy oil (124.1 mPa.s), it is acceptable to enlarge drawdown pressure under the condition of low water cut period.