The performance of nuclear fuel rod cladding tubes in reactors is affected by a combination of high temperature, high pressure, and irradiation, with their creep collapse behavior being a critical factor for the safety of nuclear power plants. This study uses numerical simulation to systematically investigate how different levels of ovality affect the creep collapse behavior of these cladding tubes. A finite element model was developed to simulate the deformation and response of the cladding tubes under conditions of high temperature, high pressure, and irradiation, and to analyze the effect of ovality on the mechanical interaction between the nuclear fuel rod pellet and the cladding. The results show that the ovality of the cladding tubes has a significant impact on their creep collapse behavior; the higher the ovality, the sooner the mechanical interaction between the nuclear fuel pellet and the cladding occurs, making the cladding tubes more likely to fail during irradiation. Moreover, the contact between the cladding tube and the pellet can reduce the subsequent deformation due to creep collapse of the cladding tube. This research provides valuable theoretical support for the design and safety assessment of nuclear fuel rod cladding tubes, highlighting the importance of controlling the ovality of cladding tubes in the design of nuclear fuel elements.