Background: The cerebral aqueduct is a narrow channel connecting the third and fourth ventricles, and the aqueductal stenosis can obstruct cerebrospinal fluid (CSF) circulation, resulting in obstructive hydrocephalus. This is associated with intracranial hypertension and clinically manifests as headaches etc. Thus, understanding the effects of varying stenosis degrees of the aqueduct on the intracranial CSF flow field is essential for revealing the pathogenesis of obstructive hydrocephalus. Methods: We utilized clinical MRI image sequences of a male volunteer and semi-automated image segmentation technique to reconstruct a complete normal CSF circulation model. Subsequently, we manually created eight ideal models representing different stenosis degrees of the aqueduct. Computational fluid dynamics (CFD) was then performed to simulate the CSF flow field across all nine models. Results: The stenosis degree of the aqueduct was positively correlated with the maximum pressure difference between the aqueduct upstream and downstream and the maximum velocity of CSF within the stenosed aqueduct. In the normal model, the maximum pressure difference was 0.84 Pa and a maximum CSF velocity 11.4 mm/s. While in the maximum stenosed model, their counterparts were 21.36 Pa and 60.3 mm/s, respectively. This indicated that the maximum pressure difference and the maximum velocity were approximately 25 times and 5 times their counterparts of the normal model, respectively. Moreover, the maximum pressure difference exhibited an exponential relationship with the stenosis area of the aqueduct and a linear relationship with the square of the CSF velocity. Conclusion: The pressure difference and velocity of the stenosed aqueduct was not apparently increased with mild stenosis with respect to the normal aqueduct, while the great aqueductal stenosis increased the risk of hydrocephalus. This study provides a theoretical framework that could be helpful to understand the development of hydrocephalus and intracranial hypertension.