A method to prepare unilamellar liposomes is demonstrated, which contains two experimental steps. (a) Water in oil (W/O) droplets are formed by sonication. (b) The W/O droplets are passed through a monolayer at the oil/water interface due to gravity or centrifugation, and transformed into liposomes. The sizes of the liposomes are 100 similar to 500 nm in diameter. The bilayer of liposome is formed layer by layer, which provides an approach to prepare asymmetric liposomes.