Objective To identify the mediating effectof social isolationon the relationship between oral health and subjective cognitive decline among elderly people in the community, to provide reference for developing targeted intervention measures to alleviate subjective cognitive decline in the elderly. Methods A total of 495 elderly people from three communities in Wuhan were selected as the research subjects. A general information questionnaire, Lubben Social Network Scale, Oral Health Impact Scale (OHIP-14), and Subjective Cognitive Decline Questionnaire 21 (SCD-Q21) were used for the survey. Results The oral health score of the elderly was (17.91±4.97) points; SCD-Q21 score was (8.33±3.87) points and social isolation score was (12.16±4.33) points. The oral health score was positively correlated with subjective cognitive decline score, and negatively correlated with social isolation score. The social isolation was negatively correlated with subjective cognitive decline (all P<0.05). The mediation effect test shows that social isolation plays a partial mediating role between oral health and subjective cognitive decline in the elderly, with the mediating effect accounting for 36.2% of the total effect. Conclusion The oral health status, subjective cognitive decline and social isolation scores among the elderly population are all at a moderate level. The social isolation partially mediates the impact of oral health on subjective cognitive decline in the elderly, suggesting that promoting oral health and reducing social isolation may be effective ways to slow down subjective cognitive decline in the elderly.