Aquifers are fully classified according to vertical velocity and the change of tracer’s concentration de- tected by radioactive isotope in borehole

and the applicability of the dilution formula is summarized completely. It is pointed that the horizontal seepage velocity in gushing aquifer can’t be obtained by the formula. For the aquifer with natural hydraulic gradient

its discharge can still be calculated by correlative well flow formulae. A method is ad- vanced to gain the coefficient of permeability with combining tracer technique and water injection experiment in a borehole. Firstly

we can measure the concentration of the tracer in the borehole along with time in natural condition

and calculate the vertical velocity and discharge. Then

we inject water in the borehole and obtain a different level in the borehole

and gain a set of value about velocity and discharge in the state. Finally

the coefficient of permeability in the aquifer is got. Moreover

the calculating formulae concerning steady flow and unsteady flow are discussed re- spectively. This simple and practical method can also be applied to sopping aquifers as such as gushing aquifers

which extends the applied range of tracer technique. At last

the effective application of this method is docu- mented by a practical example.