Dynamic behaviors in a three-dimensional confined impinging jets reactor (CIJR) under excitation were experimentally studied by a flow visualization technique at 75Re150. The effects of inlet Reynolds numbers (Re), excitation frequencies and excitation amplitudes on the oscillation behaviors in CIJR have been investigated by a particle image velocimetry (PIV) and a high-speed camera. Results indicate that the excitation in the inflow of the opposed jets can induce periodic oscillation of the impingement plane along the axis, whose oscillation frequency is equal to the excitation frequency. At Re100, the induced axial oscillation can further cause a deflective oscillation with a frequency nearly equal to the excitation, and the scale of the vortex in the impingement plane is well regulated by the excitation frequency. At Re=150, the excitation of amplitude less than 20% has insignificant effect on the deflective oscillation existing in CIJR. A semiempirical formula has been proposed to predict the oscillation amplitude of the impingement plane in CIJR under excitation. (c) 2014 American Institute of Chemical Engineers AIChE J, 61: 333-341, 2015