Abstract: At first,the basic circumstance of the paste backfilling technology is introduced,then it puts forward the basic analysis process of FLOTRAN CFD(calculation of flow dynamics).At basis of building up piping models and putting forward the basic assumption,imitate and analyze the flowing in the pipe with FLOTRAN CFD of the ANSYS software.At last,change loads of the flow or parameter,start the FLOTRAN CFD again and get a series of results,the data match basic regulation of scientical theories,which shows the science and effectiveness of this method.