The present work is dedicated to experimental measurement of internal velocity profile within a forming droplet in micro-channels. Velocity distributions are obtained by a micro-particle image velocimetry (Micro-PIV). Three liquid working systems were used to study the effects of surface properties on the droplets' internal flow field. Internal flow velocity increases and a pair of symmetrical vortices develop as the droplet grew in size. Vortices developed earlier in cases where the dispersed phase exhibited stronger wettability on the channel wall while later in cases of weak or partially wetting conditions. One of the most interesting findings was that the direction of internal circulation depends on the wetting state of dispersed phase on the channel wall. In addition, a swirling strength parameter was employed to characterize the developing vortices throughout the formation process. (C) 2016 Elsevier Ltd. All rights reserved.