Last weekend your correspondent was walking in the mountains southwest of Badaling, around the border between Hebei Province and Beijing. I saw three different snakes.
One of them had brown and white stripes and was about 30 cm long. I did not see its head. One had a triangular head, and green-brown body, with a green-and-black diamond pattern. The other disappeared too quickly to notice colors and shapes.
There is very little information online about snake species in the wild in China. Many of the Google results searching for ‘China snake species’ are news articles about snakes as food items. The image reproduced here (from Philip Colla Photography) shows a Chinese Mountain Viper (Protobothrops jerdoni), which may be the second snake mentioned above, although it seems a little too yellow.
If any Danwei readers know of information sources about snake species in the Beijing area, or can help with identification, please leave a message in the comments or email jeremy at danwei dot org.
UPDATE: Thanks to Hetoucai‘s comments to this post, Danwei has been able to compile a brief field guide to the snakes of Beijing.