According to micro-emulsification theories, Span80+Tween80+ oleic acid was chosen as the surfactant to prepare methanol-diesel micro- emulsified fuel with many kinds of concentrations ratio. The effects of different mixture ratio of surfactant, amount of methanol, different HLB and different additive on stability of micro-emulsion diesel oil were investigated in more details．As a result, the optimum conditions were found as follows: the value of m(Span80) ∶m（Tween80）∶m(oleic acid) 3∶3∶6, the amount of the surfactant 4％(wt), the additive n-butyl alcohol and the ratio of methanol and fuel oil 1∶8.