Abstract: The theory of groundwater flow system is the core conceptual framework of contemporary hydrogeology.It is very important to study the influence of different control factors to the groundwater flow system development pattern.Researches of recent years have put forward that flux upper boundary can better reveal the influence of different factors to the change of the groundwater flow system pattern.We simulate basin groundwater flow system based on flux upper boundary and study the influence of decayed hydraulic conductivity with depth to the change of groundwater flow system pattern when the flow is steady.Studies show that with the attenuation speed of hydraulic conductivity increasing,the water level raises and the velocities of the upper basin increase,and the hydraulic gradient increases.Meanwhile,the groundwater flow system is varied from complex multi-order flow system to a local flow system.The spaces of antegrade local flow systems become smaller and that of reverse local flow systems become bigger.The circular areas whose velocity is approximate to zero move to the lower left corner.