Abstract: Objective: To compare the imaging quality and radiation dose under fixed and variable exposure conditions and to determine the value of variable exposure conditions in a one-stop cranial computed tomography (CT). Methods: One hundred patients who required one-stop head CT scanning because of cerebrovascular disease at our hospital between March and May 2024 were prospectively selected and randomly divided into groups A and B, with 50 patients in each group. All patients underwent the first phase of scanning at 5~65s after contrast injection, and a total of 18 scanning phases were performed. In group A, all patients underwent the same exposure conditions for all scan phases, with a tube voltage of 100kV and tube current of 100mAs. In group B, the patients were scanned with different tube currents according to the different diagnostic purposes of each phase of the image data. The CT values and noise of the gray matter, white matter, and extra-cranial air in the cerebral hemisphere during normal scans were measured using CT post-processing workstation, and the contrast noise ratio (CNR) of the images was calculated. The CT values and noise in the intracranial artery and parenchyma were measured using computed tomography angiography (CTA) images, and the CNR was calculated. Perfusion parameters such as cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), and time to peak (TTP) in the computer-to-plate-performed image were measured, and a five-point scale was used to subjectively evaluate the image quality at each stage. The Shapiro–Wilk test was performed to test the normality of objective indicators, and an independent sample t-test was used to compare objective indicators between the two groups. The Wilcoxon signed-rank test was used to compare subjective scores. Results: The CNRp and subjective scores of the plain scan images in group B were better than those in group A. The CTA image noise in group B was lower than that in group A, and the CNRa and subjective score in group B was higher than that in group A. However, the perfusion parameters of CTP in group B did not differ significantly from those in group A (all P > 0.05). The dose length product (DLP) in group B was increased by approximately 0.65% compared with that in group A. Conclusion: Compared with the fixed exposure condition group, the image quality of the one-stop cranial CT under variable exposure conditions was significantly improved. No significant differences were observed in any perfusion parameter, and the overall radiation dose was not significantly increased, providing better image quality than that under fixed exposure conditions.