1Based on the data of Argo float, satellite altimeter merged data, and HYCOM model output, we analyzed the temporal-spatial variations of a mesoscale cold eddy in the east of Luzon Strait, and used FOR3D model to simulate the effects of this mesoscale cold eddy on sound propagation, Calculated out the transmission loss(TL) with or without the cold eddy. Result show that the presence of cold eddy led to significant variation of sound propagation. Typically, the distances of convergence zones were narrowed several kilometers, and the gain of convergence zones were inhibited about 2 dB.