The trapezoidal demisters are commonly used to remove droplets over 10 ?m in the field of natural gas purification. In order to solve the problem that the separation efficiency of the demisters obviously reduced at high gas velocity in the actual industry, the biomimetic microstructure was constructed on the surface by the wire electrical discharge machining (WEDM) technology to obtain a hydrophobic surface. Furthermore, the effects of surface wettability on the separation efficiency and pressure drop for the demisters were evaluated experimentally using atomized droplets. The results showed that the surface with biomimetic microstructure had good hydrophobic function and resistance reduction effect, which accelerated the drainage rate of liquid film. When the gas velocity exceeded 5 m/s, the liquid film thickness was relatively thin, which effectively suppressed the re-entrainment phenomenon of the droplets and improved the separation efficiency. In addition, the flow field distribution in the hydrophobic trapezoidal demisters was relatively flat, and the flow resistance was very small. The total pressure drop was only half of the demisters with hook. Therefore, the composite separation performance of the hydrophobic trapezoidal demisters with high efficiency and low resistance was optimal.