Abstract of a thesis is the brief and accurate representation of the thesis, with the important function of persuading readers to read on the thesis. So how the writer constructs the abstract and wins readers' recognition is our main focus. On the basis of Burke's Identification Theory, this paper analyzed 10 abstracts from "Nature" from content and form perspective respectively. The results show that identifications by sympathy, by antithesis and by inaccuracy are three main content identification strategies and conventional form is the main form identification strategy, which combine together to improve the objectivity and persuasion of abstracts.