The digital transformation of higher education requires a more integrated understanding of how college English teachers develop digital literacy. Existing approaches often remain fragmented, treating training, platform construction, individual learning, and institutional incentives as separate interventions. Drawing on ecological systems theory and the TPACK framework, this conceptual study identifies three structural challenges: fragmented professional agency and shallow pedagogical integration, weak collaborative learning and limited knowledge circulation, and incomplete institutional and governance support. In response, it proposes a four-level ecosystem comprising teacher self-development, professional learning communities, institutional support, and external governance with networked resources. It also develops a three-phase operational pathway encompassing diagnosis and differentiated planning, collaborative learning and classroom practice, and evidence-informed reflection and iterative improvement. The framework reframes digital literacy development from episodic training to continuous professional growth, from individual adaptation to multi-actor collaboration, and from tool-oriented evaluation to pedagogically grounded improvement. It provides a theoretical and practical reference for universities seeking to support sustainable, discipline-responsive, and ethically responsible digital literacy development among college English teachers.