Abstract: An experimental study of heat transfer in turbulent separated flow over a forward facing step is reported in this paper.The present work deals with a quite small forward facing step model (step height H=4.0mm),therefore a special technique that can change the relative locations of heat flux gauge from the step is applied successfully. The investigation is focused on two recirculation zones.Measurements of heat transfer are performed in Ludwieg Wind Tunnel by the transient technique,which demonstrates a new method of experimental research in this field.Within the range of Reynolds number 11800 to 32200,the distribution of wall heat flux and the distribution of Nusselt number are obtained.Those distributions show that the heat transfer coefficient increases to the first maximum value near the step in the front recirculation zone and the second maximum occurs at the reattachment point in the downstream recirculation zone where this point is fixed roughly at X/H=2.5 for the five different Reynolds numbers.The second maximum is larger than the first for same Reynolds number.At last a correlative equation between Reynolds and Nusselt numbers is presented.