To investigate the correlations between choroidal parameters and primary angle-closure suspect (PACS) in different age subgroups.Participants aged 50 years or older in a rural area of Daxing District, Beijing, were recruited. Swept-source optical coherence tomography was used to measure the choroidal parameters. Demographic, ocular biometry parameters and choroidal parameters were compared between the PACS and non-PACS (NPACS) eyes. Logistic analysis was performed to explore the association between the choroidal parameters and PACS.192 (26.89%) subjects with PACS and 509 (71.29%) with PACS were analysed. Subjects were divided into two groups: group 1 (50-60 years, n=286) and group 2 (>60 years, n=415). In group 1, the mean subfoveal choroidal thickness of PACS eyes was 341.82±88.23 µm and thicker than NPACS eyes (315.07±83.53 µm, p=0.035). The choroidal volume was greater in PACS eyes (10.61±2.78 mm3) compared with NPACS eyes (9.66±2.49 mm3, p=0.013). In group 2, no significant difference in any choroidal parameters between PACS and NPACS was found. Multivariate regression demonstrated that increased choroidal volume was associated with PACS (OR 1.298, 95% CI 1.117 to 1.510, p<0.001) in group 1.In the age group of 50-60 years, PACS eyes had greater choroidal thickness and volume than NPACS eyes, and the increased total choroidal volume was a predisposing factor for PACS.ChiCTR2000037944.© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.