A new testing method was used to observe on-line the dynamic wetting course of liquid resins on PE fabric. The measure procedures and data processing were introduced in detail. To aim at some applications of vinylester resins/polyethylene fiber composites, vinylester resins (VRs) were at first modified by three kinds of additives, including elastomer, liquid rubber and isocyanate-terminated prepolymer. Then the wetting behaviors of these modified resins on the surface polyethylene (PE) materials were observed. After they were modified by six kinds of elastomers, the infiltrate-steady-times of these resins on the surface of PE fabric all increased; only the contact angle of natural rubber-modified VR on the surface of PE film decreased. After VRs were toughened by three kinds of liquid rubbers, their wetting velocities all became slower and the contact angles on the surface of PE film all decreased. In addition, VRs were also modified by three kinds of isocyanate-terminated prepolymers, which were the products of different hydroxyl-terminated polymers reacted with methylene bisphenyl isocyanate and whose structures were characterized by means of GPC, DSC and FT-IR, respectively. The wetting state of these modified resins on the surface of PE materials suggested that the interfacial compatibility of modified VRs and PE fabric did not decrease at the same time when the other properties of vinylester resins changed.