Based on physical chemistry pseudo ternary phase diagram and orthogonal experimental method, the method of the component and preparation of pesticide microemulsion was discussed in detail. The heat storage and cold storage tests were used as an indicator to examine the stability of the formulations we obtained. Finally, the best formulation was obtained as follows: triazophos (2.946%), surfactant DK90 (7.232%), ethanol (4.821%), stabilizer A (0.4841%), distilled water (84.52%). Experimental results show that our method is simple, scientific and effective. It is beneficial for us to select the microemulsion formulation.