Push-pull ventilation is widely used for contaminant control in surface tanks in industrial buildings. However, existing design guidelines focus on surface tanks below 100 °C, and there is a lack of investigations on high-temperature surface tanks in the smelting industry. The characteristics of the slot jet under a high-temperature heat source can serve as valuable insights for designing push-pull ventilation systems. In this study, the jet trajectory and axial velocity are examined and analyzed, employing both numerical and experimental methodologies. The results showed that the slot jet under a high-temperature heat source can be divided into two regions based on different dominant factors: Region I (the Quasi-isothermal Jet) and Region II (the Quasi-hot Jet). Then, the Archimedes number (Ar) is introduced to quantify the relative strength between the heat source intensity and the initial momentum of the supply jet. It was found that to form a complete jet, rather than a short-circuit jet, Ar ≤ 7471 should be satisfied. Moreover, the boundary between the two regions of the jet is located approximately 0.8 times the width of the heat source. Finally, it was noted that the supply jet could better resist the influence of the heat source when Ar ≤ 4048. As a result of this study, formulas were established to describe the jet trajectory and axial velocity under high-temperature heat sources, to provide design guidance for the application of push-pull ventilation systems in high-temperature surface tanks.