Objective To explore the regulatory effect of social support on the relationship between acute cerebral infarction （ACI） in the elderly and depression after infarction. Methods Retrospective analysis of the clinical data of 115 elderly patients with ACI were admitted to the Second Affiliated Hospital of Zhejiang University Medical College from August 2021 to July 2022. National Institutes of Health Stroke Scale （NIHSS）， Self-Rating Depression Scale （SDS） and Social Support Rating Scale （SSRS） were used to evaluate severity of ACI， severity of depression and social support level in elderly patients with ACI. Pearson method was used to analyze the correlation among SSRS，NIHSS and SDS. Hierarchical regression analysis was used to explore the moderating effect of social support on the relationship between ACI and depression after cerebral infarction in the elderly. Results The average NIHSS score of 115 elderly patients with ACI was （9.08±2.11）， the average SDS score was （55.90±9.36）， and the average SSRS score was （38.10±5.64）. There were no statistically significant differences in SDS scores of patients with different gender， age， marital status， infarction site， drinking history， hypertension history， hyperlipidemia history and education level （P ＞ 0.05）. Pearson correlation analysis showed that the SDS score of elderly ACI patients was positively correlated with the NIHSS score （r=0.424， P=0.016）， and negatively correlated with the SSRS score （r=-0.469， P=0.013）. Hierarchical regression analysis showed that there was a moderating effect between social support and ACI in the elderly（β= -0.192， P ＜ 0.001）. Conclusions Social support has a regulatory effect between elderly ACI patients and post-infarction depression， and high social support can alleviate the depression of elderly ACI patients