Abstract: A splitter plate was used to suppress vortex shedding from a cylinder oscillating in stream-wise direction. The splitter plate was set on the centerline of the cylinder wake, and the control parameters were the length of the splitter plate L/D and the gap between the central position of cylinder oscillation and the leading edge of the plate G/D, where D is the diameter of cylinder. The value ranges of L/D and G/D in the test were 1.0～ 4.0 and 0.8～ 4.4, respectively, and the ranges of Reynolds number and the reduced frequency of cylinder oscillation were Re=V_∞D/v=1.01×10⁴～1.69×10⁴ and f_eD/V_∞=0～0.03, respectively. Results of smoke wire visualization and hot-wire measurement in wind tunnel show that vortex shedding from both sides of oscillating circular cylinder can be suppressed when the splitter plate is placed in a certain region called the effective zone. The effective zone area increases with the increase of length of splitter plate and decreases with the increases of Reynolds number and the reduced frequency of cylinder oscillation.