This work is aimed at the investigation of the senescence associated genes differentially expressed in rat muscle by cDNA microarray. After total RNA isolation, mRNA purification and probe preparation, the gene expression patterns of rat muscle from the old group (30 months old) and the young group (3 months old) were compared by cDNA gene chips. In the muscle of old rats there were reproducibly 127 differentially expressed genes, among which some down-regulated genes were involved in energy metabolism and signal transduction, while some up-regulated genes were related to protein degradation and cell apoptosis. Meanwhile muscle fiber atrophy with mitochondria vacuolation was found in aging rat by electron microscope.