Abstract: Based on different outer flow conditions of the gaps, someresearch on theflow and its mechanism have been discussed respectively in thispaper. A model of flow construction in deep gaps has been given. After interpreting the process of gas heat transfer in gaps in detail, a simple flow model and its computational model within the gap have been given,and its border conditions,relation curves between effected depth and outer flow parameter and certification of the computational result in light of mechanism are presented.Finally, on the basis of the result of computation certified by experiment, comparative relation curves between computational results and experimental results are given, and the mechanism causing the differences is analyzed.