Flooding has been considered one of the important issues for the limitation of performance and durability of fuel cell. The flooding in fuel cell is investigated by developing visualization system with high spatial resolution, which is designed to give close images and movies of emergence, coalesce and removal of droplets in fuel cell. It has been shown that capillary force plays dominant role in liquid removal at low flow velocity, which is a typical operating condition in fuel cell. Increasing the hydrophilic properties of side walls and front wall of flow channel will result in higher liquid spreading and removal rates, while larger contact angle on GDL surface is preferred. The spreading time on front surface could be greatly reduced by decreasing the width of the flow channel. To get a stable performance of fuel cell, the water accumulation rate should be designed to be smaller that the ability of water removal.