The composite films were prepared by using polyvinyl chloride (PVC) as film-forming matrix, and dioctyl phthalate (DOP), dibutyl phthalate (DBP), o- nitrophenyl octyl ether (o- NPOE) and diisooctyl sebacate (DOS) as plasticizers. The mass ratio range of plasticizer and PVC is 1.0 ~ 3.0, which is similar to the mass ratio range of plasticizer/PVC in ion- selective electrode films prepared by predecessors. The influence of plasticizer dosage and molecular structure on the surface structure and wettability of the films was studied by the change of contact angle with time. The results show that the change of contact angle of the plasticizer /PVC composite films with time is related to the deflection of alkyl chain in the system. DOP/PVC composite films with mass ratio of 1.0~3.0 and DBP/PVC composite films with mass ratio of 1.0~3.0 have sharp drops, and the more plasticizer content is, the earlier the occurrence of the sharp drop phenomenon appears. The plasticizer molecules in o-NPOE/PVC and DOS/PVC composite films with different mass ratios are quickly deflecting, and the initial contact angle is not much different from the equilibrium contact angle, which decreases by about 2° within 60 s. The equilibrium contact angle is related to the ratio of the number of non-polar fatty carbon atoms to the number of polar groups (A_p/P_o) of the plasticizer molecules. When the mass ratio of plasticizer and PVC is 1.5~3.0, the A_p/P_o of DOP/PVC, o-NPOE/PVC and DOS/PVC are equal, and the equilibrium contact angle is basically close to 88°. The A_p/P_o of DBP/PVC system is smaller than of the previous three, and the equilibrium contact angle is small, only 79.0°.