In　this　paper　we　extend　the　size　efficiency　model　of　Maindiratta　(1990),　which　is　distinct　from　scale　efficiency　of　DEA,　then　we　use　the　extended　model　and　the　data　of　year　2006-2009　to　evaluate　the　size　efficiency　of　Chinese　commercial　banks.　Our　study　reveals　that　almost　a　half　of　Chinese　commercial　banks　should　consider　changing　their　business　strategy　to　make　efficient　use　of　resources,　so　that　to　gain　a　higher　efficiency.　©　2011　IEEE.