Water vole is the largest individual vole. Its body length is usually more than 150mm, and its tail length is slightly more than half of its body length, accounting for about 56% of its body length. The tail is thick at the base, tapering significantly towards the end. The tail hair is short and dense, and the tail hair is about 4-5mm long, which almost covers the scales on the tail, and the tip of the tail forms a bunch of small pens. The tail is drawn forward, reaching about its shoulders.

The water vole's upper incisors are semicircular in outline from the root to the cusp. The root is at the anterior edge of the anterior orbital foramen, forming a slightly enlarged place. The root of the lower incisor foramen extends posteriorly to the base of the mandibular condyle, forming a small, not too high protrusion on its lateral side. The molars are large and thick, have no roots, and continue to grow throughout life.