A negative pressure jet intensified emulsion preparation method for emulsified diesel oil is characterized in that components of the emulsifier composition are mixed uniformly according to a proportion, the uniformly mixed emulsifier and diesel oil are dispersed by a means of negative pressure jet intensified emulsion, a stable dispersion system is obtained; assistant emulsifier and oil quality improver are added in the dispersion system according to a certain proportion, water or aqueous solution of a kind of substance is poured in the above-mentioned solution in a uniform speed, negative pressure jet intensified emulsion is performed for a certain of times, the solution is precipitated naturally for 1 to 2 days, the solution is filtered, and the obtained supernatant is emulsified diesel oil. In the method for preparing emulsified diesel oil, water or aqueous solution of a certain substance serve as materials and replace part of diesel oil to produce emulsified diesel oil; the preparation method has advantages of simple operation process, is easy to be used in a large scale and is easy to be industrialized.