A retrospective cohort study of 320 women with severe preeclampsia in China (2023–July 2025) compared early (≤ 60 min after diagnosis) and late (> 60 min) intravenous administration of labetalol. Early administration resulted in significantly greater increases in middle cerebral artery pulsatility index (MCA PI) at 60 min, 6 h, and 24 h (p ≤ 0.040) and shorter time to blood pressure control (median 60 vs. 95 min, p < 0.001). After 6 and 24 hours, both systolic and diastolic pressure were lower in the earlier group (p < 0.01). Improvement in MCA PI was inversely correlated with time to pressure control. Maternal complications (HELLP syndrome, acute kidney injury, pulmonary edema, ICU, death) and neonatal outcomes (birth weight, small for gestational age, ICU, complications, perinatal death) were not significantly different between groups. Early administration of labetalol improved maternal cerebral perfusion and accelerated pressure stabilization without worsening outcomes.