Abstract: In this paper, we selected the clear waveform data recorded by 18 seismic stations within 2° from the epicenter of Jiangsu seismic network, and remeasured the focal depth of the M_S5.0 earthquake in Dafeng sea area of Jiangsu Province by using the simple type, LocSAT and HypoSAT seismic positioning method, using the South China, the middle-south segment of Tan-Lu Fault Zone and IASP91 velocity model respectively. And the obtained depth values are compared and analyzed. The results show that the focal depths measured by the three seismic location methods are close, about 11 ± 2 km; The calculation result of HypoSAT positioning method is relatively stable, and the models of IASP91 and the middle-south segment of Tan-Lu fault zone are suitable for the calculation of focal depth in this area.