Abstract: AIM: To distinguish the commercial crude drug “wushaoshe” (Zaocys dhumnades) from its substitutes, especially when they were cut into pieces, is difficult. In order to solve the problem, the Cytb gene fragment both of “Wushaoshe” and of its substitutes together with their corresponding original animals were sequenced in the present research. METHODS: Cyt b gene fragment of about 308 bps was amplified using a pair of universal primers, L14841 and H15149. The PCR products were purified and then sequenced by silver staining DNA sequencing technique. RESULTS: DNA sequence of 246 bps Cyt b gene fragment were obtained from 22 individuals including Zaocys dhumnades and 9 other species of common colubrid snakes. Among the sequence data, 101 varied sites were found. The interspecific substitution varies from 1184% to 23.98% with an average of 16.85%. The intraspecific substitution varies from 0 to 4.06% with an average of 1.14%. The former is fifteen times of the latter. CONCLUSION: The Cyt b gene fragments were highly conservative at intraspecific level in the snake, while they were less conservative at interspecific level. Hence, the sequence of this fragment is a good molecular marker for identification of the crude snake drugs.