In this talk, we study three versions of adaptive finite element method: r, h and p-adaptive. While the first two are well developed and widely used, much less is known about the third one. By looking at some ideas and techniques used in r-version and h-version, we propose a tentative plan to construct a p-version of adaptive finite element method. The key thing makes it possible is the recently result of Bank, Xu and Zheng on generalizing gradient recovery technique for linear elements to derivative recovery for Lagarange elements of order p arbitrary.