[Objective] Blowouts and fires are extreme accidents in oil and gas field development. During such accidents, the wellhead is exposed to extreme heat from uncontrolled flames, leading to a progressive degradation of its mechanical strength. Therefore, assessing its residual strength in the aftermath of a blowout fire is essential for ensuring the safety and effectiveness of disaster response measures. To accurately evaluate the mechanical resistance of wellhead materials at high temperatures, 35CrMo, a steel commonly used in wellhead construction, is selected as the research object due to a notable gap in experimental research regarding its behavior under thermal stress. [Methods] Herein, twelve high-temperature tensile tests were conducted across four temperature levels (400 °C, 500 °C, 600 °C, and 700 °C), with three replications for each temperature, and three ambient temperature tests for comparison. The test specimens were fabricated using the Vturn S26/110 precision CNC lathe. Based on the High Temperature Tensile Test Methods for Metal Materials (GB/T4338-2006) standards, experimental tests were conducted using the microcomputer-controlled electronic universal testing machine UTM5105HB. [Results] The experimental results reveal that at temperatures ≤500 °C, a larger fracture diameter of the specimen is observed, indicating that the material keeps its high plasticity and toughness within this temperature range. Meanwhile, at temperatures >500 C, the specimen exhibits a smaller fracture diameter and obvious necking phenomenon, indicating a decrease in plasticity and toughness of the material under a high-temperature environment. Moreover, the material tends to undergo concentrated deformation and rapid fracture in local areas, indicating a shift in its fracture mode toward brittle behavior. With the increase in temperature, the stress value of the material at the same strain level shows a gradually decreasing trend. Especially in temperature ranges of room temperature to 400 C and 500C to 600 °C, the decrease in stress is particularly significant, indicating a significant decrease in the mechanical properties of the material within these temperature ranges. Furthermore, with the increase in temperature, the elastic modulus, yield strength, and tensile strength gradually decrease. Compared with room temperature, the elastic modulus, yield strength, and tensile strength are decreased by 89.5%, 92.2%, and 92.0%, respectively. This significant decrease in performance leads to a significant reduction in the structural integrity and load-bearing capacity of the material in high-temperature environments. [Conclusions] The obtained experimental data offer valuable insights for engineering evaluations of the safety and reliability of the wellheads in extreme temperature conditions, providing a reference for the development of blowout fire disposal and prevention strategies. Moreover, this work covers relevant fundamental knowledge and incorporates practical engineering application scenarios, in line with the principle of advancement, innovation, and challenge proposed by the Ministry of Education for practical courses. Such experiments can deepen students' understanding of fundamental knowledge, enhance their ability to solve practical engineering problems, and cultivate innovative thinking skills and scientific research interests. [ABSTRACT FROM AUTHOR]