Nanoparticles' phase transfer behaviors at the oil-water interface have many respects in common with lipid bilayer crossing behavior and the Pickering emulsion formation. Hence, the interfacial behavior and phase transfer behavior are intuitive indicators for the application potential of nanoparticle materials, e.g., on the emulsion formation and biomedical applications. Polymer brush modification enables nanoparticles to behave differently in hydrophilic solvent, hydrophobic solvent, and their interface region. In the present work, phase transfer behaviors of triblock polymer brush modified gold nanoparticles are explored by using coarse-grained simulations. The nanoparticles grafted with hydrophobic/weak hydrophilic/hydrophobic triblock brushes are found to have the best phase transfer performance, and the enhanced flexibility and mobility of head blocks are found to be the most vital factors. The inherent mechanism of interfacial behavior and phase transfer process are investigated and explained as perturbation effect and traction effect. According to our results, middle blocks dominate the brush morphology and decide whether NPs can be transferred into another phase. However, the inner blocks show higher dominance for the phase transfer behavior of nanoparticles restricted in the interface region, while the outer ones shows higher dominance for the nanoparticles departing from the interface region. Otherwise, interesting flat-Janus morphologies are found. Special applications in two-phase interface including emulsion stabilization could be expected. This work could provide some guidance for the molecular design and applications of polymer-nanoparticle composite materials.