This case study takes the Shenzhen Tobacco Finance Integration Subsystem Consulting and Design Project as the research object, and systematically reviews the main problems and consulting design practice faced by state-owned tobacco commercial enterprises in promoting finance integration under the “chimney-style” construction pattern of finance informatization. Centering on the control demands, tax and financial regulatory compliance requirements and business value goals of Shenzhen Tobacco, the project referred to the layered design thought of TOGAF Enterprise Architecture (EA) and the implementation path of data governance, adopted a compound methodology of “top-down design and bottom-up implementation”, and divided the whole design into five core stages: top-level planning, business domain decomposition, data integration, product architecture, and implementation and operation, forming an integrated construction path of “blueprint design—business decomposition—data integration—architecture implementation—operation iteration”. Through systematic research and diagnosis, the project set up L1 to L5 maturity grading goals of finance integration, and delivered unified top-level business boundaries, implementation routes and control standards. Following the core design principle of “business drives finance, finance controls business in return”, the project completed closed-loop process decomposition of eight standardized business domains including expense sharing, supply chain business-finance, project cost, asset life cycle, centralized capital, tax management, accounting consolidation, and budget management. Taking the SASAC “four-stream integration” standardization requirement as the core, the project built a whole-domain data system and realized automatic mapping and matching among business flow, invoice flow, capital flow and accounting data flow. The project adopted a layered and decoupled microservices architecture to build a five-layer product system of integration access layer, unified master data layer, finance core business layer, intelligent engine layer and data application layer, and accumulated five standardized engines of voucher generation, cost allocation, risk control verification, invoice-payment reconciliation and AI intelligence. Through a three-stage verification mechanism of process simulation, data consistency and compliance audit, together with a three-step landing strategy of pilot first, group batch promotion and intelligent iterative upgrading, the project delivered a series of outputs including finance integration blueprint, product architecture, data architecture, standardized business processes and operation plan, realizing the control requirements of single source, closed-loop process, forward control and cross-organization collaboration, which provides a referential consulting design path for finance integration construction of tobacco commercial enterprises and even large group enterprises.