The remodeling of chromatin is a key step in controlling and regulating the temporal expression of genes. In the senescent human diploid fibroblast, there is a specific heterochromatic structure accumulating in the nucleus in the form of punctate foci, which is termed as senescence-associated heterochromatic foci (SAHF). The histone H3 methylated on lysine 9 (K9M-H3) and Heterochromatin Protein 1(HP1) are the marker proteins of SAHF. During the process of SAHF formation, many factors such as p16^INK4a/Rb pathway and HMGA proteins play a very important role. Recent studies have shown that SAHF may suppress the expression of some E2F-target genes, thereby making the cell keep in a stable senescent state. The discovery of SAHF has provided a new biomarker for the research of cellular senescence, and it also gives us a molecular explanation for the stability of the senescent state.