Abstract: Through reflecting on the limitations of traditional department law in addressing emerging and interdisciplinary issues, field law proposes its fundamental propositions: problem orientation as the theoretical foundation, social fields as the normative basis, and domain rule as the social foundation.However, the existing theory of field law has failed to integrate into China's theoretical discourse system of legal studies, adequately comprehend the complexity of modern department law, and effectively prevent its own risk of overgeneralization.These theoretical predicaments stem from the theory of field law remaining at the inductive stage centered on specific fields, and neglect its theoretical justification.The theoretical justification of field law constitutes a process of integrating it into China's legal theoretical discourse system, comprising two components: external justification and internal justification.The external justification requires both clarifying its differentiation from department law to prevent its absorption by the latter, and revealing their complementary relationship to demonstrate field law's theoretical function.The internal justification does not against the necessity and extensiveness of interdisciplinary legal research in social fields, but rather against prematurely proclaiming it as an independent interdisciplinary legal discipline without forming a research paradigm of field law, so as to avoid a false prosperity of interdisciplinary legal studies.