An off-line plate profile gauge and a using method thereof belong to the field of metal material processing detection. The off-line plate profile gauge comprises a metering frame body, a precise moving track, a roller mechanism, a track slide frame, an upper sensor, a lower sensor, a lower sensor set screw, an upper sensor set screw, a metering arm, a connecting screw, a sampling mechanism, a track set screw and a set screw. The off-line plate profile gauge using method includes steps of vertically disposing the upper sensor and the lower sensor on the same axis of two thick surfaces of a to-be-metered steel plate, moving the two sensors along a direction parallel to the surface of the steel plate, automatically acquiring signals through sum-difference compensating measurement, and finally storing the metered results after performing a series processes on the signals. The off-line plate profile gauge and the using method thereof have the advantages of realizing fast, accurate, high-efficient off-line measuring of geometric parameters such as thicknesses, local high spot, profile, wedge and the like of cold-rolled sheet incoming material/finished products, and providing support to improving size precision of sheet products and optimizing control process in the production field.