“Reverse Mixed Ownership Reform” and the digital transformation of family firms have long been focal points in both academic and practical circles. This study focuses on the impact of state-owned equity participation on the digital transformation of family firms and further explores the underlying mechanisms. The research finds that state-owned equity participation can promote the level of digital transformation in family firms. Mechanism tests reveal that state-owned equity assists family firms in achieving digital transformation primarily through alleviating financing constraints, enhancing technological innovation capabilities, and mitigating agency problems. This study contributes to three aspects: First, it enriches research on state-owned equity participation in family firms by revealing the conduit role of state capital in the “government-enterprise-market” collaborative governance mechanism. Second, it supports mixed-ownership reform solutions in the digital economy era by offering policy guidance for government departments, strategic methods for family firms to acquire transformation resources through equity innovation, and analytical tools for financial institutions to identify state-backed investment targets. Third, it promotes multi-stakeholder collaboration in digital economic development. These contributions theoretically bridge gaps in state-capital-driven governance mechanisms, practically assist policy optimization and corporate transformation, and provide directional references for financial risk assessment in China’s mixed-ownership context.