An experimental investigation was conducted to study the effect of header and channels orientations on the two-phase flow distribution in parallel micro-channels. The parallel micro-channels was composed of a header with hydraulic diameter of 0.667 mm and three parallel channels with hydraulic diameter of 0.500 mm, all with rectangle cross sections. Nitrogen and 0.03 wt% sodium dodecyl sulfate (SDS) solution were used as the test working fluids. The inlet superficial velocities of gas and liquid varied from 0.200 to 16.0 m/s and from 0.0246 to 0.650 m/s, respectively. The fluid dynamics of two-phase flow splitting in parallel micro-channels was captured by high speed recording technique and three flow patterns were observed at the inlet. It was found that the phase distribution characteristics of two-phase flow in parallel channels highly depended on the inlet flow patterns and the orientations of header and channels. For slug flow, a uniform phase distribution was achieved in horizontal header with vertically downward channels, whereas the distribution of slug-annular flow was improved in vertically upward header and horizontal channels. For annular flow, two-phase inhomogeneous distribution reached the highest when the header was vertically downward. (C) 2017 Elsevier Ltd. All rights reserved.