Abstract: To study the oxidation and phase structure of fuel pellets for both intact and leak pressurized water reactors fuel rods with different burnup, Raman spectroscopy was used to analyze the intact fuel rods with 14 GW·d·t⁻¹ and 41 GW·d·t⁻¹ burnup as well as the leak fuel rods with 14 GW·d·t⁻¹ and 41 GW·d·t⁻¹ burnup. Evaluation of the reactivity and structural changes of the fuels based on different laser powers are provided locally. The results show that the increase in laser power would not cause oxidation of UO₂. The intact fuel rod UO₂ pellets with 14 GW·d·t⁻¹ and 45 GW·d·t⁻¹ burnup consist of UO₂, U₄O₉ and U₃O₈, and the oxidation of fuel pellet in peripheral zone is higher than that of the internal area. The leak fuel rod UO₂ pellets with 14 GW·d·t⁻¹ and 41 GW·d·t⁻¹ burnup have undergone restructuring and formed columnar grains, which consist of UO₂ and U₃O₈. The increase of burnup and leakage of fuel rods can promote the oxidation of UO₂ pellets, but the main phase structure of the fuel pellets will not change.