The work aims to characterize the effect of surfactant on the wettability of reservoir rocks surface. The mica tablet was treated with 5% simethicone ethanol solution to oilwet surface, and the distilled water and brine solution with different concentrations of single chain, dimer typed and oligomeric quaternary ammoium salt cationic surfactant were prepared. With dodecane as oil phase, the wetting angles of surfactant solution on natural mica and oil mica surface weremeasured by contact angle measuring instrument. The wetting mechanism of different types of surfactants was analyzed, and the corresponding wetting model was established. The wetting factors of different surfactants were obtained and validated throughthe experiments. The oligomeric surfactants OL1 could change the water wet surface of natural mica into oil wet surface at low concentration, andthen into water wet surface at high concentration. When the concentration of OL1 in distilled water was 0.2%, the wetting angle couldbe reversed to 141.31°(120.08° in brine) and when the concentration of OL1 was 0.5%, the wetting angle was reduced to 80.47°(85.10° in brine). The single chain surfactant SC1 could change the oil wet surface of treated mica into water wet surface. When the concentration of SC1 in distilled water was 0.5%, the wetting angle couldbe reversed to 65.78° (65.51° in brine). The effect of dimer typed surfactant DI1 on wettability was weak. The wetting model hada strong universality and matched with the experimental results. Different types of quaternary ammonium surfactants have different effects on the wettability of rock surfaces, and the wetting model can reflect the wetting behavior of surfactants on the surface of mica surface.