[Zhang BingKai] Fuyang Normal Coll, Dept Phys, Fuyang 236041, Peoples R China
; [Dai BenZhong
; Zhang Li] Yunnan Univ, Dept Phys, Kunming 650091, Peoples R China
; [Cao Zhen] CAS, Inst High Energy Phys, Key Lab Particle & Astrophys, Beijing 100049, Peoples R China
BL Lac object S5 0716+714 is a well-studied object. In this paper, the available optical (BVRI) data of this source are compiled, and the B-, V-, R- and I-band light curves are constructed. Each of them is analyzed by means of the discrete correlation function (DCF) method, the structure function (SF) method and the z-transformed discrete correlation function (ZDCF) method. The results imply that there is a possible periodic variation of 1211 days in each passband light curve. The source varies violently and complicatedly, and exhibits a brightening trend in the light curves.