Biosurfactants are used as a solution to the use of synthetic surfactants in Enhance Oil Recovery (EOR) process which are not safe for environment. One of the requirements for biosurfactants in EOR is having the ability to reduce the value of the interfacial tension (IFT) to a minimum of 10-3 mN/m. To meet the requirement, the performance of biosurfactants can be improved by having it interact strongly with nanosized support material. In this study, the stability of the free monorhamnolipids (without silica) and the monorhamnolipids-silica nanoparticle complexes at the decane-water interface at 300 K was studied by in silico method. Component density analysis shows that monorhamnolipids and monorhamnolipids-silica nanoparticle complexes diffuse to the decane-water interface. Trajectory analysis of the simulation boxes showed that the complexes were more stable at the decane-water interface. Based on the interaction analysis of the hydrophilic groups as well as hydrogen bonding, the complexes stability on the interface is caused by the strong hydrogen interaction between monorhamnolipids and silica that have more stable properties at the decane-water interface. This causes the complexes are more effective in reducing the IFT of decane and water with a decrease of up to 1.6 mN/m.