Yen Shih-si worked his way up from the ranks--from a basic patrol officer, to district captain, to tri-county police chief, to dean of the Taiwan Police Academy, to Taipei City police chief, and finally to his present position.
由一毛二的警員幹起，歷任三個分局的分局長、三個縣的警察局長、警察學校教育長，而後擔任五年多的台北市警察局局長，以迄現職。