This study undertakes a comprehensive analysis of energy storage harmonics within the context of gigawatt-level electrochemical energy storage power plants. The investigation delves into identifying and comprehending the principal sources of harmonics inherent to energy storage power plants, subsequently scrutinizing the potential deleterious implications arising from harmonics. The study employs advanced simulation software modeling techniques, grounded in a specific gigawattlevel energy storage power plant scenario, facilitating an in-depth exploration of the harmonic attributes intrinsic to such energy storage systems. Additionally, the research proffers strategic interventions aimed at mitigating the presence of abnormal harmonics. Rigorous empirical validation of the efficacy of these proposed harmonic mitigation strategies is conducted, thereby contributing to the establishment of their effectiveness. Furthermore, the study furnishes valuable insights and recommendations that serve to guide the refinement of harmonic optimization designs for expansive-scale energy storage power plants, enhancing their operational efficiency and grid compatibility.