The squirrel belongs to the genus Squirrel in the suborder Squirrels of the order Rodentia. Body size is usually medium-sized, is the cold temperate coniferous forests and mixed forests in the typical representative of animals. It has strong limbs, sharp claws with hooked ends, and usually weighs about 350 grams, with females slightly heavier than males. Squirrels are slender and lithe, with a body length of about 18-26 centimeters and a long, thick tail that is more than two-thirds of the body length but less than the body length.

Tail hair is dense and long and fluffy, limbs and front and rear feet are longer, but the front limbs are shorter than the hind limbs. The ear shell is well developed, and when folded forward it reaches the eye, and in winter there is a tuft of long black hair at the end of the ear. The back of the body from the end of the muzzle to the base of the tail, the side of the body and the outside of the limbs are brownish-gray, the base of the hair is grayish-black, and the tips of the hair are brown or gray. The abdomen is white from the back of the lower collar to the base of the tail and on the inside of the limbs. The dorsal and ventral surfaces of the tail are brownish black with a gray hair base and brownish black tips. The muzzle, cheeks, and underparts are as dorsally colored but bluish gray, the ear shells are blackish gray, and the winter coat has large tufts of black hairs. Individual coat color varies widely, including greenish gray, gray, brownish gray, dark gray, and blackish brown. With regional differences, coat color also varies, such as Liaoning squirrels are grayish in color, while squirrels in the south of China are darker in color. In addition, the fur color is also affected by the season, winter fur gray or gray-brown, summer fur black or dark brown.