Abstract：Rising atmospheric carbon dioxide concentrations have made ocean acidification a serious global environmental issue, posing a major threat to marine biodiversity, ecological structure, and ecosystem function. As seawater continues to absorb anthropogenic carbon dioxide, it alters the marine carbonate system, leading to a decrease in pH and a reduction in carbonate ion concentrations, which in turn affects the calcification processes of various marine organisms. Among these, benthic foraminifera are shelled protozoa widely distributed in marine and estuarine sediments; they are particularly vulnerable due to their calcium carbonate-rich shells. Because their shells are extremely sensitive to changes in the carbonate system, benthic foraminifera are widely recognized as ideal indicator organisms for monitoring ocean acidification and its ecological impacts.This review systematically examines the physiological and ecological response mechanisms of benthic foraminifera under ocean acidification conditions, focusing on four key aspects: changes in species distribution and community structure; morphological responses of the shell; changes in shell chemical composition, particularly elemental composition and stable isotopes; and effects on physiological metabolism, including calcification, growth, and reproduction. Extensive evidence suggests that ocean acidification leads to severe dissolution of calcareous shells, stunted growth, and an increased incidence of shell deformities. Furthermore, studies have documented significant changes in the elemental ratios and stable isotope characteristics of shells, which may compromise their reliability as proxy indicators for paleoceanography. In terms of physiological metabolism, acidification regulates the growth and survival of foraminifera by modulating calcification-related enzyme activities, disrupting energy allocation budgets, and altering symbiotic relationships with photosynthetic partners. Despite these advances, most current studies remain limited to short-term, single-factor laboratory experiments and are unable to capture the complex interactive effects that arise when multiple environmental stressors act simultaneously in natural settings—such as the combined effects of warming, oxygen depletion, and nutrient pollution. Therefore, future research should prioritize multi-factor stress experiments, long-term field observations under natural acidification conditions, and multi-omics integrated studies to elucidate the underlying molecular mechanisms. Establishing standardized research protocols is also urgently needed. Collectively, these efforts will facilitate a more comprehensive understanding of benthic foraminiferal responses to ocean acidification and enhance their value as reliable environmental indicator species in a changing ocean.