The utility model relates to the technical field of roads, and in particular relates to a device for testing a coefficient of linear expansion of cement concrete. The structure of the device mainly comprises a hard outer cylinder body, a soft inner cylinder body, a blanket layer and end seals; the soft inner cylinder body is inserted into the inner side of the hard outer cylinder body; the blanket layer is mutually bonded with the inner wall of the soft inner cylinder body; and two end seals are respectively arranged at two ends of the hard outer cylinder body. Compared with the prior art, the device provided by the utility model has the characteristics of simple structure, accurate testing results and the like.