The purpose of this study was to develop oil-in-water (o/w) and water-in-oil (w/o) microemulsion formulations for improving the oral absorption of poorly water-soluble drug, puerarin. During screening and preparation, the influence of the oils, surfactants and co-surfactants on the solubility of puerarin was investigated in details. The pseudo-ternary phase diagrams were developed for various o/w and w/o microemulsion formulations to indentify the most efficient microemulsion region, respectively. After the step-by-step experiments mentioned above, the ultimate optimized o/w and w/o microemulsion formulations were formed with 3.1％ ethyl oleate, 18.5％ Cremophor RH 40, 9.2％ 1,2-propanediol, 69.2％ water and 45.0％ ethyl oleate, 22.5％ soybean lecithin, 22.5％ ethanol, 10.0％ water (w/w), respectively.The o/w and w/o microemulsion formulations were characterized by droplet size, viscosity, electro-conductivity and stability study. During the bioavailability study of those microemulsions, the plasma concentrations of puerarin were determined using an HPLC method following gavage administration in rats. There was a significant improvement in the oral bioavailability of puerarin compared with suspension formulation (P<0.05). The relative bioavailabilities of o/w and w/o puerarin-loaded microemulsions were 4.42-fold and 8.31-fold compared with puerarin suspension, respectively. These results indicated that o/w and w/o microemulsions are promising drug delivery systems for puerarin by the oral route.