This study aimed to evaluate changes in macular vascular density and macular function in patients with high myopia cataract (HMC) after phacoemulsification surgery, using optical coherence tomography angiography (OCTA) and multifocal electroretinography (mfERG). Patients with cataracts scheduled for phacoemulsification surgery were divided into a high myopia group (axial length > 26.5mm) and a control group (22mm < axiallength ≤ 24.5mm). OCTA examinations were performed before surgery and at 1day, 1week, 1month, and 3-6months post-surgery, while mfERG was conducted before surgery and at 3-6months post-surgery. A total of 38 patients were included, of whom 20 were HMC patients and 18 were control patients. The macular vascular density significantly increased after phacoemulsification surgery in both groups, while foveal avascular zone area decreased significantly (HMC group: all p < 0.01; control group: all p < 0.05). Mean changes in macular vascular density were significantly greater in HMC patients than in the control group at 1day after surgery (all p < 0.05). The amplitude density and latency of P1 wave in all macular rings (Ring1-5) did not differ significantly before or after surgery in either group (all p > 0.1). Phacoemulsification may not affect HMC patients' macular mfERG responses within 3-6months post-surgery, but it may influence macular microcirculation. HMC patients should be closely monitored after surgery, as their retinal vascular density may fluctuate substantially in the early postoperative period.