Aging has been identified as one of the risk factors for chronic disease, and the onset and development of many chronic diseases are closely related to gut immune dysfunction in the elderly. Aging profoundly affects the intestinal immune system and the homeostasis of intestinal flora. We have reviewed the changes in intestinal mucosal immune function that occur with aging, including Toll-like receptors (TLRs), T cells, B cells and inflammatory cytokines such as IL-6, TNF-α and IFN-γ. Age-related changes in typical gut microbiota and their metabolites were discussed. Aging leads to changes in the composition and diversity of the gut microbiota. With advancing age, intestinal bacteria such as Bacteroides, Bifidobacterium and Clostridium butyricum undergo significant alterations. These changes lead to a decline in the metabolites produced by the gut flora, including short chain fatty acids (SCFAs), bile, indole and indole derivatives. As a result, the homeostasis of the gut microbiota becomes disrupted, leading to an imbalance in the intestinal microbial ecosystem. The interaction between the intestinal flora and its metabolites and the intestinal immune system has been studied and a high correlation between the intestinal flora and the immune function of the intestinal mucosa has been proposed. Under normal circumstances, a healthy immune system and gut flora are mutually reinforcing and promote the health of the host. However, with age, the integrity of intestinal mucosa and the homeostasis of intestinal flora are disrupted, resulting in a decline in the immune response and regulatory capacity and an inability to respond effectively to various exogenous insults. Meanwhile, the ongoing damage to the immune system further exacerbates the imbalance in the gut flora. Changes in the gut flora of the elderly affect the diversity and levels of key immune molecules such as defensins and immunoglobulin A (IgA). Abnormal expression of immune molecules in the gut also leads to changes in the composition of the gut microbiome, affecting gut health and potentially increasing the risk of disease. The metabolites of intestinal flora interact with intestinal receptors, activate relevant signalling pathways, directly regulate immune cells and control the immune system, influence the intestinal barrier and intestinal immune functions, and exert immunoregulatory effects on the intestine. As the relationship between gut flora and immune aging becomes clearer, future research can explore strategies for targeted regulation of gut flora for anti-aging and immune enhancement. In this paper, we further explore the regulation of gut flora and gut immune function by dietary intervention and fecal microbiota transplantation (FMT) to achieve the goal of delaying immune aging. Dietary intervention promotes the growth of beneficial bacteria by adjusting the structure of the elderly’s diet and supplementing with microbial preparations, maintaining the intestinal barrier and reducing chronic inflammation. FMT involves the transplantation of faeces from healthy individuals into recipients to improve mucosal integrity and promote microbial diversity. This paper has discussed the complex mechanism between aging, gut flora and immune response, highlighted the research progress of gut flora anti-aging methods, with the aim of providing a reference for research on targeted gut flora regulation to promote gut mucosal immune function for health promotion and anti-aging.