The invention discloses a composite plate test part automatic assembly device. The device is characterized in that the device comprises a composite plate transferring apparatus, a bottom plate liftingtype material frame, a grinding mechanism, a vacuum box, a turnover apparatus, a rotating mechanism, alignment mechanisms, a welding apparatus and an aluminum profile support. A plate material is conveyed onto a flow line through the composite plate transferring apparatus and the bottom plate lifting type material frame; the plate material is ground through roller brushes and aligned once, then abase plate and a covering plate are assembled through the turnover apparatus; the rotating mechanism rotates continuously by 90 degrees so that the second alignment mechanism and the welding apparatus performs peripheral sealing welding on a composite plate; after welding is finished, a composite plate assembled body transferring apparatus conveys a composite plate assembled body onto the flow line; and assembling is finished. By means of flow line automatic production of a composite plate blank, labor work is reduced; the production rate can be improved to the great degree, and the accuracyand surface cleanliness which are required during rolling can be improved, and the cost is reduced; and thus the composite plate combination effect is enhanced, and the combination strength is improved.