The invention is applicable to the field of mobile terminals, and provides a method, a system and a mobile terminal for realizing one-handed mobile terminal operation. The method comprises the following steps of: receiving a command for starting a one-handed operation mode; according to the command, zooming out a screen to a preset size; and displaying a reduced screen thumbnail on an original screen in a picture in picture mode. Through starting the one-handed operation mode, the screen thumbnail which is smaller than the original screen is displayed on the original screen of the mobile terminal in the picture in picture mode. The operation on the thumbnail is mapped to the operation on a large screen, so that the operation on the thumbnail equals to the operation on the large screen, and moreover, the operation on the screen except for the thumbnail can also be responded. The operation of the large screen is not influenced on the basis of controlling the big screen through the thumbnail; and thus, a one-handed operation function of a large-screen mobile phone is realized, good experiences are brought to users, one hands of the users can also be released to do other things, so that conveniences are brought to the users. The one-handed operation mode cannot influence the displaying effect of the large-screen mobile phone, and cool experiences are realized in the way that small-scope operation controls large-scope display.