Based on the signal theory and using Luckin Coffee and Xiaomi as the focal brands, this research explores the mechanisms and boundary conditions of brand alliance patterns on brand relationship quality through three experiments. The results show that, compared to visual co-branding, consumers have a more innovative perception and stronger brand relationship quality in ingredient co-branding; the mediating role of brand experience varies with alliance patterns and product types. In ingredient co-branding, compared to visual co-branding, the mediating effects of affective experience, behavioral experience, and cognitive experience are significant, while sensory experience and relational experience partially mediate the relationship; For shopping goods versus convenience goods, the mediating effect of relational experience is more pronounced; Perceived innovativeness and brand experience serve as chain mediators in the relationship between brand alliance patterns and brand relationship quality; the level of consumers’ lay rationalism will weaken the positive impact of perceived innovativeness on brand experience.