More and more companies are developing customer service by building Smart Community Service Brand Platforms (SCSBP). However, the impact of digital platform functions on sustainable brand relationships, and the mediating mechanism of customer’s emotional cognition are still unclear. The functional value of digital services in the property service industry focuses on three dimensions, including service efficiency, personalization, and social interaction. Regarding consumers’ emotional cognition aspect, we investigate value consistency and brand image. The empirical analysis findings suggest: (1) the functional value of smart community service has a significant positive impact on consumers’ emotional cognition and is positively related to the construction of sustainable brand relationships; (2) consumers’ emotional cognition of smart community service is positively related to the sustainable brand relationship; (3) consumers’ emotional cognition plays a complete mediating role between service efficiency and sustainable brand relationship, demonstrating a partial mediating role between personalization and social interaction aspects of functional value and sustainable brand relationship. This study contributes to the customer-based sustainable brand relationship theory in the digital service environment and provides a reference for companies to continuously improve the SCSBP and customer-based brand construction.