Biosurfactant is produced by a certain microorganism to reduce surface tension. Microbial enhanced oil recovery (MEOR) is one of the many applications of biosurfactant. However, the biosurfactant for MEOR needs to be able to withstand the extreme environment of oil reservoirs with high temperature and high salinity. Halomonas meridiana BK-AB4 is a halophilic bacterium obtained from the Bledug Kuwu crater in Central Java, Indonesia. The similarity of both environment condition indicates the potential to produce suitable biosurfactant. This study evaluates the potential of Halomonas meridiana BK-AB4 in producing biosurfactant compared to several bacteria isolated from the crater. The blood agar test of Halomonas meridiana BK-AB4 exhibited greenish discoloration around the colony, indicating the ability of type α-hemolysis. The interfacial tension was measured using the Du Nouy ring method to represent the biosurfactant activity, with the results of 0.014 dyne/cm. These results showed that Halomonas meridiana BK-AB4 has a very good potential for producing biosurfactant for MEOR. The optimum time of the culture starter for production is 6 hours, as determined from the bacterial growth curve.