Abstract: By the method of visible observation,experimental study on heat transfer characteristics of stratified fluid is made in three different pipes,at the same time,computational model on heat transfer is built,and mechanism of heat transfer in density lock is analyzed.The results show that the work fluid can be divided into three zones from top to bottom:mixing layer,interface layer,and conduct layer.In mixing layer heat is mainly transported by convection,and transported by conduct in interface layer and conduct layer.In addition,the result of study on different pipes indicates that the honey comb channel in density lock can efficiently curb the disturbance,lessen the thickness of mixing layer and decrease the heat transfer through density lock.