Abstract: To obtain the characteristics of the first mode internal solitary wave dynamic structure and temporal variation in the continental slope region of northern South China Sea, ocean current data observed with ADCP from May 5 to June 3, 2021 are used and 179 first mode internal solitary waves are identified. Analysis of the internal solitary waves shows that, the vertical structure associated with the internal solitary waves are of double-layer, the current in upper layer is northwestward while that in lower layer is in opposite direction, and the reversal of current direction occurs at 100-150 m. The maximum ocean current were observed in the upper layer with amplitude of 60-120 cm/s. Influenced by internal tide, internal solitary waves exhibit two major periods, semidiurnal and diurnal periods, and propagate northwestward as wave trains with recurrence period of 20-30 minutes. These findings are useful for improving the understanding of the spatial-temporal variation of internal solitary waves, and provide theoritical references for underwater engineering.