Abstract: The 280 mm x 380 mm cast bloom temperature of steel U75V for heavy rail in walking beam reheating furnace has been traced and measured by using Thermophil STOR measure system (black box) at steel works, and the data are treated by Origin software to get the curves of cast bloom heating temperature, temperature increasing speed and difference of temperature between bloom surface and center etc. Results show that the average heating temperature of cast bloom is 1 220 °C , as heating time in furnace is more than 180 min, the control temperature in soaking zone should decrease by a- bout 20 °C； the effect of water-cooling beam in furnace on temperature of bloom bottom surface is obvious, therefore the control temperature of lower section in soaking zone is higher 20 °C than that of upper section ； at current heating condition, it meets the requirement of heavy rail production that temperature differential between center and surface of finished heating bloom along the thickness direction is less than 20 °C and the cast bloom temperature is more than 1 200 °C.