Students’ mental health is a crucial issue related to the country’s future and population quality. Currently, student psychological crisis intervention faces multiple practical dilemmas, such as broken responsibility chains, fragmented resource networks, and insufficient collaborative capabilities. Based on Bronfenbrenner’s ecological systems theory, this paper constructs the core metaphor of “Fishpond Co-Governance”, comparing the student psychological ecosystem to a “fishpond”, and clarifies the legal roles and core responsibilities of four main subjects—schools, families, medical institutions, and communities—under the framework of laws and regulations such as the Mental Health Law. On this basis, from three dimensions of collaborative mechanisms, system resources, and subject capabilities, the paper systematically proposes practical paths for building a “law-based collaboration” governance system. It aims to provide school administrators with a clear theoretical framework and action guide to transform collaborative concepts into operable governance efficiency, promoting campus psychological crisis intervention from scattered response to systematic and comprehensive ecological governance.