Direct underwater observations, using a remote operated vehicle, on substrate types and distributions of macrobenthos were made at depths between 35 and 120m in southern Taiwan. Three substrate types were classified, i. e. blocks and boulders, rubbles and gravels, and sandy bottom. No existing coral reefs were found below 40 m and the majority of the substrates were covered by sand, The rocky substrate with scattered blocks and boulders supports the richest fauna and flora including many forms of gorgonaceans, antipatharians, hydroids, sponges, bryozoans, ascidians and crustose coralline algae. The most dominant macrobenthos on rocky substrates are fan and whipshaped gorgonaceans and antipatharians. The soft coral, Dendronephthya spp., was dominant on the substrate of rubbles and gravels, The sandy bottom was depauperate in fauna and flora. Hydroid colonies including large plumularid hydroids were often found on sandy bottom. The depth limit of hermatypic corals and algae in southern Taiwan were at depths between 70 and 80 m. The distribution of corals and algae in deep water habitat is likely restricted by low light intensity, heavy sedimentation, the deficiency of firm substrates and high benthic hydraulic energy of the environment.