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Groundwater models are critical for simulating subsurface hydrological processes and guiding informed policymaking for groundwater management. However, the widely applied groundwater models typically use regularshaped grids to discretize aquifer systems and require that the directions of the grid edges are aligned with the hydraulic conductivity tensor. Such rigorous requirements for spatial discretization have constrained the models' application in aquifer systems with anisotropic hydrogeological characteristics. To address such limitations, we develop an improved groundwater flow model based on the multipoint flux approximation (MPFA) method in this study. The new model allows us to use arbitrary-shaped polygon grids to discretize aquifer systems and relaxes the rigorous requirement of the alliance between polygon edges and hydraulic conductivity tensor. The functionality and performance of the new model are demonstrated by comparing the output between our model, MODFLOW, and analytical solution in four case studies with various hydrogeological conditions. In a real-world watershed with complex-shaped boundaries, our model outperforms the conventional groundwater model in boundaries. The modeling results show that our model can yield accurate simulation of subsurface hydrological processes in aquifer systems with complex-shaped boundaries. Furthermore, our model can provide a more flexible discretization solution to couple surface water and groundwater model in integrated hydrological model development.地下水模型对模拟地下水文过程、支撑地下水管理的科学决策至关重要。然而，当前广泛应用的地下水模型通常采用规则形状网格对含水层系统进行离散，且要求网格边的方向与水力传导张量（hydraulic conductivity tensor）方向保持一致。这种对空间离散的严苛限制，制约了模型在具有各向异性水文地质特征的含水层系统中的应用。为解决上述局限，本研究基于多点通量近似（multipoint flux approximation, MPFA）方法开发了一款改进型地下水流模型。该新型模型支持采用任意形状的多边形网格对含水层系统进行离散，同时放宽了多边形网格边与水力传导张量方向需对齐的严苛要求。本研究通过在四种不同水文地质条件的案例中，对比本模型、MODFLOW模型与解析解的模拟结果，验证了新型模型的功能与性能。在一个具有复杂边界的真实流域案例中，本模型在边界处理方面优于传统地下水模型。模拟结果表明，本模型可准确模拟具有复杂边界的含水层系统中的地下水文过程。此外，在综合水文模型的开发中，本模型可提供更为灵活的离散化方案，用于地表水与地下水模型的耦合。