Abstract: During the automated fiber placement of carbon-fiber-reinforced polyetheretherketone composite material (CF/PEEK) thermoplastic prepregs, achieving a wrinkle-free steering radius is strongly governed by the synergistic regulation of process parameters, making it a critical factor that constrains the design window for low-defect placement paths. However, quantitative characterization of the feasible domain of the wrinkle-free steering radius under coupled process parameters and a mechanistic understanding of wrinkle defect evolution remain limited. In this paper, a process envelope of the wrinkle-free steering radius for CF/PEEK prepregs was established, and the intrinsic relationship between wrinkle morphology evolution and interfacial constraint conditions under process regulation was revealed. A process simulation model integrating a hypoelastic constitutive model with cohesive contact properties was developed, with its reliability validated via 2.5D image characterization. Subsequently, the response surface methodology was employed to determine the effects of temperature, compaction force, and laying speed on the interlayer tack performance and tow width, based on which the process envelope was constructed using wrinkle-free placement criteria. The results demonstrate that enhanced interfacial constraint shifts the steering-induced compressive deformation from out-of-plane bending toward localized in-plane shear, accompanied by a transition in wrinkle morphology from arcuate undulations to localized linear compression. Through coordinated regulation of the process parameters, the minimum wrinkle-free steering radius was reduced from 1216.61 mm to 926.93 mm, corresponding to a 23.8% reduction. A process envelope for the wrinkle-free steering radius of CF/PEEK thermoplastic prepreg was established, providing a theoretical basis for layup path design and defect control on complex curved surfaces.