Triangular structure is used as basic shape of artificial structures for generating the upwelling current in order to make rich fishing ground at sea. Artificial upwelling current could bring the deep sea water containing a lot of nutrients from the bottom up to the surface. The purpose of this study is to examine the flow characteristics around underwater triangular structure with various stratification parameter. An experimental study was carried out for the triangular structure model in the circulating water channel to investigate flow characteristics by flow visualization method. A velocity fields around the underwater structure were measured by particle image velocimetry(PIV). The experimental results showed that the upwelling effect at the back and upper region of the structure could be best when the water depth was 2 times of the structure height and the stratification parameter was approximately 3.0. These quantitative data will be useful to determine the functional efficiency cf artificial upwelling structures.