For any digital chaotic sequence generator, evaluating periodic characteristics which exist in only part of domains of binary chaotic sequences is extremely difficult. In this paper, we present a method which we name the binary sequence period detection (BSPD). The BSPD is a novel detection which evaluates the periodicity in a binary chaotic sequence, by which both the accurate-periodic phenomena and periodic phenomena in part of domains can be detected. Moreover, any periodic phenomenon pattern of a binary sequence can be located by the BSPD method. The experimental results show that the BSPD can detect and extract the periodic phenomena of the classical Logistic chaotic sequence generators.