Abstract: AimTo study the effect of hyaluronic acid chitosan-based microemulsion (HAC-ME) on the permeability of blood brain barrier(BBB) by using Evans blue (EB) as the indicator. MethodsA formamide extraction-ultraviolet spectrophotometry method was employed to determine the concentrations of EB in each of the tissues. The in vivo distribution of HAC-ME groups containing EB in mice and the fluorescence intensity and diffusion domain of brain slices were all studied. ResultsContrasting to the common microemulsion (ME), HAC-ME at the lower concentration of HAC (<5 mg·mL^-1) could further improve the transporting of EB across the BBB while EB concentration in other tissues decreased, and t_max was delayed about 30 min. ConclusionHAC-ME could facilitate the transporting of EB across the BBB and it was concentration dependent. While the brain targeting absorptive capability of HAC-ME was enhanced.