This paper proposes a structured description and discretized modeling method for aero-engine complex piping systems based on the Lindenmayer system (L-system). By leveraging the grammatical rewriting rules and parametric extensions of L-system, a tree-like structural description and geometric discretization of piping are achieved, addressing the structural characteristics of both typical pipes (e.g., I-type, L-type) and complex three-dimensional pipes (e.g., bifurcated pipes, helical pipes). The proposed framework is further extended to integrate physical attributes, enabling the unified expression of geometry, topology, material, and cross-sectional properties within a single symbolic system. Furthermore, by comparing the dynamic characteristics of continuous and discrete structures in free modal analysis, the feasibility and accuracy of equivalent modeling using discrete straight segments are demonstrated. The discretization granularity is discussed, and the method’s adaptability for different analytical precision requirements is established. This approach successfully unifies the geometric description, structural discretization, and physical property assignment of complex piping, providing a new structured and automated pathway for rapid modeling, dynamic analysis, and optimization design of aero-engine piping. The inherent parameterization and automation advantages of the L-system also open avenues for automatic layout generation, integration with intelligent optimization algorithms, and future development towards a comprehensive “geometry compiler” for CAD/CAE interoperability and digital twin applications.