Abstract: Compared with laser and hot air heating, infrared (IR) heating has outstanding advantages such as low cost and low pollution, and is an ideal heat source for automated fiber placement (AFP) forming of low-melting thermoplastic composites. However, the coupling of IR-assisted AFP process parameters is strong, and the effects on forming accuracy, defect formation and macroscopic properties are still unclear, and there is a lack of data accumulation of related processes. In this paper, for the IR-assisted AFP in-situ forming process, continuous glass fiber reinforced polypropylene composite unidirectional laminates were prepared by regulating the lay-up pressure and speed, and the effects of lay-up temperature and pressure on the thinning effect, warpage deformation, crystallinity and porosity were investigated, and the influence of structure and defects on the macroscopic mechanical properties such as bending strength and interlaminar shear strength were further investigated. The results show that: Too high temperature leads to severe thinning effect, too low leads to high porosity; Too high forming pressure causes severe warpage and fiber deformation and reduces interlaminar shear strength. Through reasonable control of temperature and pressure, the porosity can be reduced to 1%, which meets the requirement of 2% threshold for civil-composite components; The bending strength of specimens is up to 466 MPa, which is only 6% lower compared with hot pressing forming.