Abstract: The proadipocyte line of spotted sea bass (Lateolabrax maculatus) provides a new in vitro model for exploring the regulation of adipocyte differentiation and adipocyte deposition in fish and the related molecular mechanisms. This experiment aimed to establish a proadipose cell line for the spotted sea bass. Peritoneal adipose tissue was digested using collagenase and pancreatic enzyme, and after multiple passages, a preadipose cell line was successfully obtained following 150 times of culture cycles. karyotype analysis showed confirmed the maintenance of a normal phenotype in the cell line during long-term culture. Additionally, the mitochondrial cox1 and cytb genes were further used to identify the cell line as originating from the spotted seabass. The established cell lines were subjected to transfection with the pEGFP-C1 plasmid, resulting in observable green fluorescence, indicating their suitability for studying the expression of foreign genes. Furthermore, when cultured with different concentrations of oleic acid, the cell lines exhibited prominent lipid droplet aggregation after 3 days, reaching its maximum accumulation after 7 days. Oil red O staining demonstrated that the cells could differentiate and mature normally after 7 days of induction with 400 μmol/L oleic acid. In summary, this experiment successfully established a preadipose cell line for the spotted sea bass, characterized by typical morphology and normal differentiation. This cell line serves as valuable experimental material for future studies on adipose cell differentiation and adipose deposition in fish.