private secretary        
noun [ C ] uk/ˌpraɪ.vət ˈsek.rə.tər.i/ us/ˌpraɪ.vət ˈsek.rə.ter.i/
 私人秘书
a secretary who works for a business manager or official, dealing with their letters, filing, etc.
  (部长的)私人助理
someone whose job is to help a government minister