Understanding social determinants of HIV late presentation with advanced disease (LPWA) beyond individual-level factors could help decrease LPWA and improve population-level HIV outcomes. This study aimed to examine county-level social determinants of health (SDOH) with HIV late presentation. We aggregated datasets for analysis by linking statewide HIV diagnosis data from the South Carolina (SC) Enhanced HIV/AIDS Reporting System and multiple social contextual datasets (e.g., the American Community Survey). All adult (18 years and older) people with HIV diagnosed from 2014 to 2019 in SC were included. Linear mixed models with forward selection were employed to explore the association of county-level SDOH with the county-level three-year moving average percentage of LPWA and average delay time from HIV infection to diagnosis. Around 30% of new HIV diagnoses were LPWA in SC, and the mean delay time for people with LPWA was approximately 13 years. Counties with more racial residential segregation had longer average delay time (Adjusted beta = 5.079, 95% CI: 0.268 ~ 9.889). Regarding other SDOH, the increased percentage of LPWA was associated with fewer Ryan White centers per 100,000 population (Adjusted beta = -0.006, 95% CI: -0.011~-0.001) and higher percentages of the population with less than a high school education (Adjusted beta = 0.008, 95% CI: 0 ~ 0.015). Reducing county-level disparities in LPWA requires multifaceted interventions addressing multiple dimensions of SDOH. Targeted interventions are needed for counties with more Black residential segregation, fewer Ryan White centers, and higher percentages of less than high school education.