N6-methyladenosine (m6A), as the most common RNA modification at the post-transcriptional level, plays a role in various pathophysiological processes. However, its underlying mechanism in skin aging remains enigmatic. Here, we identified that fat mass and obesity-associated protein (FTO) serves as a protective factor against skin aging. FTO expression is downregulated in aging skin tissues and senescent fibroblasts. Furthermore, the depletion or inhibition of FTO exacerbates dermal fibroblasts senescence and accelerates skin aging. Additionally, RNA-seq combined with MeRIP-seq revealed that lysine acetyltransferase 8 (KAT8) is the downstream target of FTO. FTO deficiency leads to an increase in m6A levels and a decrease in mRNA stability of KAT8 in a m6A-YTHDF2-dependent manner. Notably, our integrated analysis of m6A sequencing and acetylation proteomics links changes in heterochromatin structure with aging. Mechanistically, KAT8 depletion leads to heterochromatin loss and the subsequent aging by acetylating remodeling and spacing factor 1 (RSF1) at K1050. Overall, our finding reveals a pivotal role of FTO-mediated m6A modification in the skin aging by regulating KAT8/RSF1-involved heterochromatin formation. It provides new insights into the mechanisms and strategies for delaying aging and improving healthspan.