Abstract: he velocity and propagation characteristics of three internal solitary waves observed by mooring system are analyzed and compared with numerical experiments to study the resonance mechanism of terrain and background current. The mode-1 internal solitary waves ( with wavelengths of 6.4 km and 3.3 km) are all concave internal solitary waves and have similar propagation speed and maximum amplitude. For horizontal flow direction structure, the flow in upper layer is northwestward while that in lower layer is southeastward. The downward and upward flow before and after the crest of internal solitary wave with wavelength of 3.3 km are more obvious. The vertical structure of zonal velocity of mode-1 and mode-2 internal solitary waves calculated based on resonance mechanism is basically consistent with the observation, and the depth of the maximum zonal velocity is comparable to the observed, the differences are 5 m and 12 m, respectively. The propagation speed of internal solitary wave calculated based on resonance mechanism is in the same order as calculated by the KdV equation, which are 0.66-1.21 m/s and 0.79-1.40 m/s, respectively.