The optimal dehydration rate of two cylindrical cyclone separators were compared under the water cut of 95%, 90%, 80% and 70% at the inlet, by changing oil-water mixing flow rate and split ratio. The experimental results show that when the inlet water cut is 95%, 90% and 80%, the optimal dehydration rate of the cylindrical cyclone with orifice vortex finder is 12%~22% higher than the cylindrical cyclone without orifice vortex finder. And the pressure drop between the inlet and the overflow increases 3~52 kPa. When the inlet water cut is 70%, the optimal dehydration rate of the former has little difference with the latter, but the maximum pressure drop between the former and the latter is 68 kPa. Under different experimental conditions, the pressure drop between the inlet and the underflow is not obvious, and the former is slightly higher than the latter. At the same time, when the inlet water cut is constant, the relationship between the optimal split ratio and oil-water mixing flow rate is consistent with the dehydration rate.