Experiments were carried out in a wave flume on internal solitary wave (ISW) of depression-type propagating over a submarine ridge in triangular shape. Tests were arranged in series from combinations of submarine ridges in different height and ISW in different wave amplitudes. The resultant wave motions were found differing from that of surface gravity waves. Experimental results suggested the blockage parameter can be applied to classify various degrees of ISW–ridge interaction, i.e., for weak encounter, for moderate encounter, and for wave breaking. In addition, three categories of ISW–ridge interaction were also employed by the relationship between the degree of blocking and dimensionless wave amplitude .