The assembly process of nanostructures plays a crucial role in controlling the morphology of nanomaterial in a microemulsion system. However, controlling the assembly process of nanostructures becomes complex and difficult, due to the multiple factors of microemulsion system. Herein, we report a facile synthesis of amorphous caddice-like silica NWs by a self-assembly process in an oil-in-water (O/W) microemulsion system. In our method, the mass ratio of tetraethoxysilane (TEOS) to dimethylbenzene (DMB) would directly control the morphologies of silica nanostructures. Interestingly, the proper low-concentration TEOS in oil phase favors the formation of silica NWs due to the self-assembly of nanosized oil droplets with silica porous shell, driving by the surface tension of oil droplets. The mean diameters of NWs could be slightly adjusted from 67 nm to 82 nm by prolonging reaction time. The as-obtained silica NWs exhibited an excellent adsorption capacity and rapid adsorption rate for methylene blue dye due to the negatively charged hydroxyl groups and high specific surface areas.