In this study, the safety of the driving gear reducer of ESW(essential service water) traveling sea water screen was evaluated through seismic analysis. Mode analysis of gear reducer was performed for reliability of analysis. Seismic analysis was performed in operating basis earthquake(OBE) and safe shutdown earthquake(SSE), which were applied as design condition using floor response spectrum( FRS). The maximum strain of gear reducer under OBE and SSE were 20.4 ${mu}$ and 33.6 ${mu}$, respectively. The maximum stresses were 2.42 MPa under OBE condition and 4.36 MPa under SSE condition, which were smaller than the allowable strength of material.