Abstract: The change in the electrical resistance of a carbon fiber felt upon loading and unloading was investigated. The resistance is highly sensitive to deformation, which increases or decreases reversibly under loading or unloading within the elastic deformation regime. The resistance versus load has satisfactory linearity and repeatability, which can be used to measure the load on the carbon fiber felt with a high accuracy. The carbon fiber felt pretreated by electric baking has a better repeatability than does the untreated sample. Carbon fiber felt can be used as a new sensor element to provide online reliable information about the deformation of a concrete structure.