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The ultrastructures of the ventral scales from Trimeresurus stejnegeri, Gloydius brevicaudus, and Sinonatrix annularis were observed by means of atomic force microscopy. The reducing-resistance mechanism of the ventral scales surface was analyzed. The results showed that the ultrastructures of three ventral scales were formed by arraying microfibrils, micropits and pits periodically. The ultrastructures of the ventral scales surface, such as the interval distance of the rows, the length of the microfibrils, the diameter and the number of the micropits and etc. are different in different inhabited environment. The length of the microfibrils decreases and the number of the micropits increases gradually from the terrestrial to the aquatic. The real contact-area between the ventral scales and the ground is reduced due to the microfibrils, which causes the decreasing of the adherence force in the sliding motion. The hydrophobia of the ventral scales surface reduces the adherence force.