The rise of bacterial antibiotic resistance poses a serious threat to both aquaculture and public health, increasing the safety risks of consuming aquatic products. Therefore, the search for new antibiotics has become a critical global priority. Marine microorganisms are considered promising sources for novel drug discovery due to their vast diversity. In this study, an endophytic fungus isolated from the Cyclina sinensis was selected and evaluated for its potential as an antibiotic producer. Polymerase chain reaction (PCR) amplification followed by gel electrophoresis and genetic sequencing was performed, and the resulting sequence was compared with the NCBI database for species identification. Both liquid and solid-state fermentation methods were employed, with extracts obtained using solvents of varying polarity. The antibacterial activity of the extracts against Gram-positive and Gram-negative bacteria was assessed using the paper disc diffusion method, comparing differences in inhibition levels. Thin-layer chromatography (TLC) was then used to observe variations in secondary metabolites between liquid and solid cultures. Subsequently, the metabolites were preliminarily separated using Sephadex LH-20 column chromatography. Fractions showing similar TLC patterns were combined and re-evaluated through antibacterial assays to identify bioactive fractions. These active fractions will be further analyzed to elucidate their chemical structures and evaluated for potential pharmaceutical applications.