wide-eyed         
adjective uk/ˌwaɪdˈaɪd/ us/ˌwaɪdˈaɪd/
 睁大眼睛的
having your eyes open much wider than usual
  轻信的;单纯的
too willing to believe and admire what you see or are told
  At that time, I was still a wide-eyed youngster. 那时候我仍然是个单纯的孩子。