An electronic device includes a storage unit, a touch display unit and a central processing unit. The central processing unit includes a control module, a searching module, and a spit-screen module. The control module generates a first window on the touch display unit to display a text document when the text document is opened, and determines a selected text of the displayed text document by a user according to touch positions when the touch display unit is touched. The searching module searches occurrences of the selected text in the text document, and the control module stores the searched text in the storage unit. The spit-screen module displays each occurrence of the selected text on a second window produced thereby with a size thereof smaller than that of the first window. A related method is also provided.