Artificial reefs (ARs) are structures constructed on the seabed to attract and concentrate fish and to potentially improve and rehabilitate coastal ecosystems. In order to investigate the hydrodynamic characteristics of ARs, a series of model experiments of cubic artificial reefs are carried out in the flume. The model reefs are made of acrylic material with different shapes of opening and various open-area ratios. The hydrodynamic forces of the models are measured in the experiments. The changes of drag coefficient with respect to the open-area ratio and the flow-facing angle of attack are investigated and discussed respectively.