Abstract: The critical flow rate obtained by speed sensitivlty testing of clastic rock cannot be directly used to determine the water flood intensity for oil field development,and to forecast the deposit position of mechanical impurity and suspended matter existing in injection water.This paper presents some special equations,which can be used to convert the measured critical flow rate to the water intensity suitable for this fault,and to forecast the deposit position of mechanical impurity and suspended matter,and gives a detailed computation for the scaling quantity produced by the combination of injection water and formation water in reservoir conditions.It has an important significance for the reservoir protection during waterflooding development of Jiao 2 fault block.