Abstract: The preparation of nanofluids has been researched by many scholars for its excellent performance in heat and mass transfer. This paper reviews the preparation of nanofluids，summarizes the current methods of preparation，and analyzes the influence factors in the preparation. It is considered that the preparation method of using ultrasonic dispersion supplemented with dispersant is the more practical and workable solution in experimental study. pH value，the type and amount of dispersant are the main factors impacting the stability of dispersion. The development direction of the preparation of nanofluids and the factors to be considered in ultrasonic dispersion are proposed.