The wake flow characteristics of a spherical bubble against the interface contaminated degree are deeply investigated at moderate Reynolds number (Re = 25-200) based on the 3D rear stagnant cap model. The interface contaminated degree is controlled by changing the magnitude of the cap angle, for theta = 0-180 degrees. It is found that the vortex size does not change obviously when theta = 0-67.5 degrees; when theta > 67.5 degrees, it decreases until it is equal to zero when theta > 135 degrees. The variations of vortex size and separation angle are related to the deceleration of fluid near the lee face of the bubble. The vortexes display the 3D characteristic due to the skip of pressure coefficient component in the flow direction at the leading edge of the stagnant cap when theta = 45 degrees, 67.5 degrees, 112.5 degrees and 135 degrees. (C) 2017 Elsevier Ltd. All rights reserved.