Abstract: The present invention discloses an oil-in-water emulsion containing no surfactant, which comprises a metabolizable oil phase, an aqueous phase and oil-water amphipathic solid particles dispersed in the aqueous phase and having biocompatibility, wherein the oil phase comprises squalene or/and tocol; the aqueous phase is any one selected from the group consisting of purified water, water for injection, glycerine aqueous solution, buffering salts aqueous solution or clinically usable transfusion, or the combination of at least two selected therefrom; the solid particles have an average particle size in a scale of from nanometer to micrometer. The emulsion of the present invention can be used as vaccine adjuvant, drug delivery carrier or sustained/controlled-release carrier, and have the controllable properties. The resultant emulsion is stable, avoids the use of surfactants and can reduce the human poisoning and environmental pollution.