In the process of transporting high temperature molten iron, the temperature drop of molten iron produced by torpedo tanker will directly affect the subsequent process. Adding insulation cover is an important measure to reduce the temperature drop of molten iron and improve the efficiency of iron and steel production. Taking a 320 t torpedo tank in a steel plant as the research object, a vehicle-mounted capping device was designed to analyze the thermal insulation characteristics of molten iron in the capping torpedo tank under actual working conditions. The results show that: (1) The vehicle-mounted capping device can realize remote loading of the tank cover, and the method is more flexible. In the case of an emergency that the lid cannot be opened, the molten iron can be flushed off the lid to complete the loading, and the molten iron transportation of the covered torpedo tanker is safer. (2) Compared with the molten iron without capping, the temperature of the molten iron can be increased by 8 °C after the whole capping. After adding an insulated cover, the thermal insulation effect is remarkable, so it is advisable to cover and transport. The research results provide a reference for further reducing the temperature drop of molten iron.