This paper investigates the lexical system in the short story collection The Endless Field by writer Nguyen Ngoc Tu through the theoretical lens of Ecolinguistics—an interdisciplinary field at the intersection of linguistics and ecology. Utilizing statistical, classification, and semantic analysis methods, the study examines a total of 368 ecological lexical units, categorizing them into five distinct semantic fields: (1) Words denoting regional ecological space (17.12%); (2) Words denoting biological entities (42.39%); (3) Words denoting weather conditions (20.92%); (4) Words denoting ecological changes (8.70%); and (5) Words denoting human ecological impacts (10.87%). The findings demonstrate that this lexical system not only vividly recreates the riverine landscape of the Southern region and incorporates a dialect rich in regional identity, but also possesses high artistic efficacy in enhancing expressiveness and blurring the boundary between humanity and nature. Through this linguistic framework, the study highlights profound warnings about environmental degradation driven by rapid urbanization, while conveying a humanistic message regarding the symbiotic, sustainable harmony between humans and the ecosystem.