The pen-tailed tree rat is a species of wild mouse that is slightly larger than the house mouse. The pen-tailed tree rat is generally about 12cm in length; the tail is very long and monochromatic, and the tail end has long hairs like a pen, which is easy to distinguish from the house mouse. The snout is slightly blunter than that of the mouse, and the whiskers are very long, up to 50mm or more. The tail is longer than the body. The first toe of the fore and hind limbs has no claws and has flat nails, and is opposite to the other four toes, with well-developed toe pads.

The pen-tailed tree rat often perches on the trees among the bamboo forests or semi-arboreal life. The pen-tailed tree rat in Hainan Island, collected at an altitude of about 1000m in the Wuzhi Mountain forest area, is a primitive arboreal species that inhabits the mountain dense forest environment. A female rat can give birth to 4 litters a year, with a gestation period of 19-21 days, with 1-4 cubs per littermate, and the pen-tailed tree rat can live for more than 3 years.