BACKGROUND: Ability of liver can remove harmful substances and make liver cells proliferate to maintain its functions.Elders are apt to be affected by stress result to liver injury.This study was to detect the expression of apoptosis promoters (Caspase3, Caspase9, Bax), apoptosis inhibitor Bcl-2 as well as antioxidative molecules GSH and SOD in elderly and young-middle aged dogs, and to explore the possible connection between aging and liver function, so as to provide theoretical base for liver protection among elderly clinically.