ABSTRACT Layup defects in automated fiber placement weaken laminate mechanical properties, making their prediction and avoidance crucial but underexplored. This study develops a mass‐spring‐dashpot system considering tow orthotropic anisotropy and viscoelasticity. Additionally, a numerical algorithm is proposed to simulate the layup process and defects, validated through experiments. The proposed system and algorithm incorporate mold surface, layup path, layup process parameters, and tow mechanics, enabling accurate simulation of defect generation during the layup process. In Case 1, the 2nd and 3rd tows exhibit maximum bridging heights of ≈12 mm with bridging lengths of ≈100 mm, while the 4th tow shows a maximum bridging height of ≈23 mm with a bridging length of ≈150 mm. In Case 2, folds of ≈1.6 mm and wrinkles of ≈1.3 mm are observed. The corresponding experimental measurements are 11.5/105/20/154.2 mm for Case 1 (heights/lengths for the 2nd–3rd and 4th tows) and 1.52/1.45 mm for Case 2 (folds/wrinkles), showing good agreement with the simulations. Furthermore, simulating a single tow requires ≈50 s per 10 mm of roller advance, consuming a relatively small amount of computing time. This system and algorithm allow rapid parameter adjustments, reducing defects and improving layup quality.