The hot spring snake is a small and medium-sized snake with a total length of 780-1000 mm. The male hot spring snake is 715 mm long and the female is larger than 820 mm. The ratio of tail to body length is 0.28 (0.27-0.30) for male hot spring snakes and 0.24 (0.23-0.25) for female hot spring snakes.

It is named the hot spring snake because the hot spring snake likes to live near the hot spring. The head and neck of the hot spring snake are clearly distinguished, the head and back are gray-green, the head and ventral surface are light yellow, the trunk and the back of the tail are olive green, and there are three rows of dark brown patches, one of which is the largest. The two outer edges of the dorsal scales are gray-green, forming several fine vertical lines of alternate depths. There is a gray light stripe behind the eye from the lower retro-orbital scale, through the upper edge of the 7th and 8th upper lip scales, obliquely to the corner of the mouth, and extending backward to connect with the longitudinal stripe on the side of the body. Maxillary teeth 21-24, gradually increasing backward.