Tritium storage and conveyance tank is composed of 1st/2nd storage tank, three different insulating layers(polyurethane form, polyethylene form and ceramic board), and conveyance tank. For the characteristics of temperature gradient by tritium decay heat in tritium storage and transportation tank, temperature gradient experiment and code simulation by Heating7 were carried out. And the results were compared and analyzed. From experimental results, the temperature in 1st storage tank increase to maximum 70 ℃. But code simulation results by HEATING7 showed higher value.