An apparatus for preparing compound dispersoids of hydrophobic nanoparticles and surfactants, comprises a water supply pipeline, a compounding mixing pipeline and an aggregating pipeline; the compounding mixing pipeline comprises an ultrasonic dispersion instrument and a liquid storage tank connected in series into a loop, and a second plunger pump allowing unidirectional circulation of materials is arranged between the ultrasonic dispersion instrument and the liquid storage tank; the water supply pipeline is connected to the top of the ultrasonic dispersion instrument; and the aggregating pipeline is connected to a discharge end of the liquid storage tank.