Pressure drop measurement and flow visualization was performed in multi-ported rectangular channels with 0.5 mm hydraulic diameter. The working fluid was HFE-7100. An experimental facility as an closed loop was set and the measurement accuracy was verified by single-phase flow experiment which was less than 4% deviation from theoretical value. Measured pressure drop showed a similar trend of variation with respect to the change of vapor quality. Also, the visualized flow patterns presented that the flow patterns were significantly affected by the variation of vapor quality and mass flux.