Abstract: Objective To prepare and determine the proportion of the components of lidocaine microemulsion. Methods Pseudoternary phase diagrams of the prepared lidocaine microemulsion with different Km (surfactant/cosurfactant) were generated to determine the optimal Km according to the size of the microemulsion area. The diameter and its distribution range, viscosity, electric conductivity and refractivity of lidocaine microemulsion drop was determined, and the appearance and system type of the microemulsion was observed using electron microscope. Results Maximum microemulsion area in the pseudoternary phase diagrams was obtained with the Km of 3, and the drop size of the microemulsion averaged 29.8±14.4 nm (with up to 98% of the drop size ranging between 15.1-45.5 nm and 2% between 77.9-261.3 nm). At 25 ℃, the viscosity, electric conductivity and refractivity of the microemulsion was 25 mPa·S,130 μs/cm and 1.473, respectively, and the lidocaine microemulsion was identified to belong to O/W type. The microemulsion drop appeared in spherical shape of heterogeneous sizes in a multi-disperse system. Conclusion The optimal proportion of the components in lidocaine microemulsion can be obtained by analyzing pseudoternary phase diagrams, and the drop size, distribution, shape and system type can be determined or observed through Maerwen Zetasizer combined with electron microscopic observation.