Abstract: The configuration of internal solitary wave (ISW) over a ridge terrain will largely increase the uncertain factors threatening the safety for marine architecture and submerged vehicle. Laboratory experiments are conducted to examine an ISW propagating over a ridge terrain and its interaction with a submerged slender body in a large-type gravity stratified fluid tank. The evolution characteristics of the ISW is measured by using multi-channel conductivity-probe arrays and dyeing identification method, and its action on the body exerted by the ISW is measured by a set of three-component force sensor. The experimental results have shown that when an ISW of depress propagates over a ridge terrain its wave configuration will be changed significantly, including that its amplitude will increase on the windward side of ridge, its lee side will be up at the top of ridge and its wavelength will be longer on the leeward side of ridge. Furthermore the configuration change of the ISW will affect obviously the characteristics of the action on a slender body, including that the downward force becomes larger distinctly on the windward side of ridge, the upward force is more significant at the top of ridge and the effective time of the action on the body becomes longer at the leeward side of ridge. Therefore, the body movement trend can be judged roughly based on the force behaviors, i.e. the largest sinking will happen on the windward side of ridge and the stronger surging towards the direction of ridge will do on the windward side of ridge.