Objective: To establish a method of screening solid-type surfactants. Method: When surfactants reached critical micelle concentration(CMC)

particle size of systems changed remarkably.we defined three parameters of S1

S2 and E

S1 was size when surfactants concentration was lower than CMC

S2 was size when surfactants concentration was higher than CMC

E=S1/S2.E value was the key to screen surfactants.Particle size and Zeta potential of microemulsions was determined

its shape was investigated by transmission electron microscope

its irritation was evaluated by rabbit eye irritation test. Result: Relative strength of emulsifying ability was in the order of cremophor RH40> Kollicoat IR> PVA> β-CD> PEG4000> SLS> poloxamer407> poloxamer188> arabic gum> PEG-CHO modified gelatin B> bone gelatin B.Microemulsions was prepared with cremophor RH40 as surfactant

its particle size was 38.50 nm

Zeta potential was-18.13 mV

its shape was round up and uniform.This microemulsion had no irritation in male rabbit eyes for 7 days. Conclusion: This approach to screen surfactants is reasonable and feasible.