The invention provides a large-size rectangular reflection lens clamping device. The device comprises a matrix and a front baffle plate connected with a front end of an upper transverse plate of the matrix, a pressing plate is arranged at a lower side of the upper transverse plate of the matrix, and the pressing plate is connected with the upper transvers plate of the matrix through a bolt; multiple threaded holes and through holes are uniformly distributed on the upper transverse plate of the matrix, and the threaded holes and the through holes are arranged at intervals; an adjusting rotary knob is screwed into each threaded hole, and the bottom thereof is contacted with the pressing plate. The invention discloses a large-size rectangular reflection lens clamping device; the lens adopts an upper-lower clamping way, the lens is mounted on a lens frame from left to right; after the lens is mounted in place, the lens is tightly supported through the upper rotary knob to realize the lensclamping; the lens dismounting process is simplified, the dismounting and maintenance and like related operations of the large-size rectangular reflection lens under the special environment can be realized, and the reflection lens and the lens film-coating can be effectively protected.