Abstract: Territorial spatial planning provides the fundamental spatial guarantee for advancing Chinese modernization, and specialized plans have become an essential implementation-support component within this system. This paper examines the renewed objective orientation and conceptual links of territorial spatial planning under Chinese modernization, focusing on the evolving transmission content between city- and county-level master plans and specialized plans. Drawing on modularity theory, it analyzes the theory’s connotations, structural features, and applicability, and proposes a modular transmission system for the master-specialized territorial spatial planning framework. At the practical level, the paper reviews cases and technical standards for specialized-plan transmission, argues for constructing system submodules through catalogue-based list management, and strengthens horizontal coordination and vertical transmission through an efficient organizational model for planning transmission, thereby meeting the requirements of strategic-goal implementation. Based on Shenzhen’s modular planning-transmission practice, the study further analyzes the operating mechanism and transmission model of ecological-space planning, with the aim of informing modular transmission pathways and implementation mechanisms for master-specialized territorial spatial planning.