Abstract: The flow around cylinder is one of the classic research issues of fluid mechanics. The modification of the cylindrical geometry will affect the cylinder’s pressure distribution and near wake flow structures. The present study on slotted cylinder has some certain values in engineering applications such as vortex generator in flow meters and heat convection. Large eddy stimulation based on 3D Fluent code was carried out for cylinders with slit, with respect to test model of ratio of slit width to diameter s/d=0.15 on five different Reynolds numbers (Re=1500,3000,4400,5837,7200). By the means of qualitative flow visualization and quantitative PIV experiments, the flow patterns between the slit and the shedding vortex of the baseline and included. The results of numerical simulation agreed well with the experimental measurement. The experimental and computational results show that the flow in the slit demonstrated periodic motion, this oscillating ventflow has greatly altered the near wake flow features. The periodic oscillation in the slit has enhanced the periodicity of the flow around circular cylinder; consequently, the slotted cylinder exhibited an increase in shedding vortex frequency and Strouhal number compared with their baseline case at the same Reynolds numbers. Meanwhile, The wake of the slotted cylinder presented obvious three dimensional features.