We investigated the general circulation around the Korea-Tsushima Strait and submesoscale eddies [O(1–10) km diameter] persistently generated behind the Tsushima Island, based on hourly and 2-km spatial resolution velocity data of the global submesoscale numerical simulation outputs (MITgcm llc4320). As the cross-correlation coefficients between subsurface currents and surface currents was over 0.7, we employed surface current data to analyze the island eddy. $M_2, K_1, O_1$ and $S_2$ are four dominant tidal frequencies around the surface of the Korea-Tsushima Strait. We detected where the surface vorticity changed their signs. Furthermore, we identified the spatial and temporal structures of the surface circulation associated with island wakes using Empirical Orthogonal Function (EOF) to check the island eddy generation period. We established that the generation frequency of the surface island wakes was within a range from 0.2 to 0.5 cycles per day (2–5-day period). The principal components in the 2nd mode in the EOF analysis revealed similar periodicity. The cross-correlation coefficient between the vorticity sign change line, and the principal components in the 2nd mode was 0.6; they had 0.8 coherence from approximately 0.2 to 0.5 cycles per day frequency. Also, the vorticity generation frequency had seasonality, and eddies were more frequently generated from April to November.