Radioisotope logging technique is an effective method to evaluate groundwater movement.Moving with the water

the isotope tracer distributes differently in different flow states.According to the depth and time distribution of radioactivity

flow state of the groundwater can be determined.In this paper

different flow states

i.e. laminar flow

turbulent flow and mixing flow

are analyzed

and calculation of the flow velocity is discussed.Also

we discuss how to distinguish the laminar flow part and turbulent part in a mixing flow.If one judges the flow state incorrectly

the error of flow velocity will be huge

hence the importance of flow state analysis.Finally

some problems in the practical projects and measuring methods are concluded.