Dental impressions are widely used in the field of oral restoration. The materials are used for making impression in oral cavity. In order to measure the thickness of impression for reference in clinic, the real impressions are taken as the object for studying. Through optical method, charge-coupled device (CCD) is used for collecting the grey image of cutting section of the impressions which are located in the same plane with steel dividing ruler. According to convert relationship between dividing ruler and pixels collecting grey image, the thickness of impression specimens can be obtained. The results show that the optical method used for measuring thickness is feasible to the task and the precision can reach micro dimension. The experiment method and technique can also be provided for measuring thickness of similar tissue engineering materials.