The largest black-headed sword snakeThe overall length is about 578 mm. Black-headed sword snakeThe head is large and clearly distinguished from the neck. The back of the head is dark black, with two black spots on the back, the upper lip scale is white, and the lower edge is mixed with black spots. The head and abdomen are yellowish-white with fine black and brown spots., span>The back is dark brown or dark brown, and there is a tan line from the back of the head to the back of the body, but the lines gradually become less obvious at the back of the body,The abdomen is gray-green or gray-white, with many slender black spots juxtaposed on both sides of the abdominal scales.

Black-headed sword snake has anterior orbital scale 1, retroorbital scale 2, temporal scale 2+2, and anterior inferior temporal scale is larger , wedged between the seventh and eighth upper lip scales, the upper lip scales are 3-3-8. The dorsal scales have 17 rows on the body, smooth and without edges, the ventral scales are 171-187, the anal scales are divided into two, and the lower caudal scales are 63-125 pairs. In addition, the black-headed sword snake lives at the foot of the mountain by the stream, where the grass is rocky and chaotic, and it is difficult to find. The food is relatively simple, mainly feeding on small lizards and occasionally other small snakes.