Abstract: The complex spatial heterogeneity of functionally graded materials(FGM) makes it challenging for traditional modeling approaches to accurately characterize their internal gradient features, and existing methods often suffer from poor compatibility with additive manufacturing processes. To address these problems, an FGM modeling and path planning method was proposed based on a mesh surface heat diffusion model algorithm. The proposed method first performs layer-wise processing on a three-dimensional model, where gradient source points are selected within each slice. The mesh-surface heat diffusion algorithm is then employed to simulate the material property gradients within each layer. Subsequently, scalar field contour lines reflecting variations in material composition are generated from the computed gradient field to guide the path planning for FGM additive manufacturing. The experimental results using an aero-engine turbine blade as the research object demonstrate that the proposed approach can achieve high-precision modeling and representation of internal material gradients in complex components, while maintaining excellent compatibility with additive manufacturing processes. This provides an efficient and feasible solution for the digital design and manufacturing of FGM.