The synthesis of octenyl succinyl ${eta}$-gucan (OSA-${eta}$-glucan) was carried out and its interfacial properties at the oil-water interface and in emulsion systems were investigated. An aqueous ethanol system as a reaction media was used to facilitate the synthesis process; 10% (w/w) ethanol found to be the best as it showed a maximum degree of substitution (DS: 0.0132). FT-IR showed a characteristic absorption spectrum at $1736cm^{-1}$, indicating the esterification of octenyl succinyl groups to ${eta}$-glucan backbone. As for interfacial tension measurements, it was decreased with increasing concentration of OSA-${eta}$-glucan in the aqueous phase and when NaCl was added to aqueous OSA-${eta}$-glucan solution in the range of 0.01 M to 0.1 M and also when pH was raised (pH 3 ~ pH 9). In systems of emulsion stabilized with OSA-${eta}$-glucan, fat globule size found to decrease with increasing concentration of OSA-${eta}$-glucan, showing a critical value of about $0.32{mu}m$ at 0.5 wt%. When the OSA-${eta}$-glucan emulsions were stored, it was found that fat globule size was increased with storage time and particularly pronounced increase was observed in emulsion with 1% OSA-${eta}$-glucan, possibly due to depletion flocculation. Results of creaming stability evaluated by light scattering technique showed that it was more stable in emulsions containing smaller fat globule size. Surface load of OSA-${eta}$-glucan in emulsions increased with increasing concentration of OSA-${eta}$-glucan, suggesting a multilayer adsorption.