This chapter explores the codification philosophies and methodologies of the Eco-Environmental Code in China, focusing on the integration of sustainable development as the core logical framework. It adopts a systematic approach to align the Eco-Environmental Code with sustainable development principles, guided by international legal frameworks. The research utilizes comparative legal analysis and case studies to provide a comprehensive overview of China’s codification efforts. The findings highlight the significance of a unified legal framework in advancing ecological civilization and enhancing legislative coherence in China. The General Part of the Eco-Environmental Code is constructed upon common principles derived from existing environmental laws, while the Specific Parts should focus on establishing administrative regulation, balancing rights, and government-led market regulation systems aimed at social, ecological, and economic sustainability. Given that the regulatory frameworks in both the General Part and the Specific Parts encompass behavioral patterns that entail distinct legal consequences, the codification of the Eco-Environmental Code should articulate relevant legal liabilities and associated applicability, guidance, and procedural regulations throughout.