Abstract: In order to carry out hot water flooding test after steam injection in BQ-10 block of Gucheng oilfield,it is necessary to make clear the distribution status of heat loss.Therefore,the study on heat loss calculation by water injcetion has been carried out.The factors,such as the thickness of the ground line thermal insulation layer,its materials,in different seasons,different hot water flow,wellbore heat insulation and water flooding time,on influencing temperatures during the process have been mainly analyzed.In the end,the optimal ground line temperature and insulation parameters of wellbore have been put forward and four temperature values of each node during hot water flooding have been determined,which provides theory basis for engineering design in the next step.