Compared to adults, the infant head exhibits significant differences in both material properties and structural composition, yet far fewer studies exist on infant head biomechanics. Sutures and fontanelles, as integral soft tissue structures of the infant skull, allow flexibility and accommodate head growth during development. However, their influence on infant head responses to external forces remains inadequately studied, which hinders the advancement of infant traffic safety measures, pediatric head injury diagnosis, and forensic assessments in cases of suspected abusive head trauma. Addressing this research gap, we aim to study the influence of suture and fontanelle morphology on infant head biomechanical response under impact using finite element (FE) simulation. For this, we first developed an automated algorithm for generating FE models with variable suture and fontanelle morphologies, tailored to the morphological characteristics of different suture and fontanelle shapes. The biomechanical influences of these variations were systematically investigated, including the impact acceleration curves and the skull fracture patterns. Furthermore, we investigated the role of accessory sutures, a critical factor but often-overlooked in biomechanics research. The results show that variations in suture and fontanelle morphology significantly influence the biomechanics of the infant head. In particular, fractures were more likely to propagate along accessory sutures in the parietal bone, leading to linear skull fractures. In summary, this study offers a comprehensive understanding of the impact loading of infant sutures and fontanelles, highlighting the importance of considering the suture and fontanelle morphologies when assessing pediatric head injuries for pediatricians, biomechanics researchers, and forensic experts.