斷層可能是有助於地下水流動的高滲透性通道，或是阻礙地下水流動的低滲透性障壁，因此斷層的水力特性影響地下水的流動，所以研究斷層的水力特徵分析非常重要。前人發展二維解析解，推求在鄰近斷層區進行抽水試驗時，抽水洩降反應的變化，藉此反推斷層的流通係數，假設斷層寬可忽略，且斷層的補注率，與水頭差成正比。本研究中以三維的MODFLOW模擬含水層-斷層-含水層系統的抽水洩降變化，對照MODFLOW與簡化解析解，兩者推估的抽水洩降，比較驗證忽略斷層寬的適當性。結果顯示斷層寬會影響斷層的補注量，所以忽略斷層寬後，簡化解析解有高估或低估斷層流通係數的風險。 Fault can function as high-permeability pathways that enhance groundwater flow or as low-permeability barriers that impede groundwater flow and as a consequence may exert a strong influnce on hydroulic head distributions in faulted aquifers. Therefore, it is important to hydrogeologically characterize such fault in many practices. To provide the hydrogeological characterization, conduction of a pumping test in the neighborhood of fault zone is proposed to determine the fault zone transmissivity by previous researchers based on the analysis of drawdown behavior using a simplified analytical solution. The simplified analytical solution assumed the fault zone width is neglected and the recharge rate from the fault to the aquifer is assumed to be proportional to the head difference. In this study, a three-dimensional MODFLOW is used for the simulation of the drawdown evolution during a pumpin test behavior in an aquifer-fault-aquifer system. The drawdown evolutions obtained from the MODFLOW are compared to those from the analytical solution to test the validity of simplification. Results show that the simplified analytical solution may overestimates or underestimate the fault zone transmissivity.