The invention relates to a laser frequency conversion coupler with nonlinear optical crystals based on a multi-sheet structure, which comprises N nonlinear optical crystals, wherein N is an integer not less than 2. The nonlinear optical crystal is provided with a light beam incident face and an emergent face in a flat shape, and a coupling prism is arranged on the light beam incident face or on the light beam incident face and the light beam emergent face at the same time; the c faces of the N nonlinear optical crystals are adhered into a whole by using optical cement or ionic bonding; the a axes of the N nonlinear optical crystals are parallel to one another and are aligned up and down with the alignment degree no more than 1 degree, and the c axes of the N nonlinear optical crystals are parallel to one another and are aligned up and down with the alignment degree no more than 0.1 degree. In the invention, the N nonlinear optical crystals KBBF (KBe2BO3F2) with very thin thickness are adhered into a whole by using optical cement or ionic bonding, the increase of the KBBF crystal thickness enables the crystal to be more practical, and the laser frequency conversion coupler of the nonlinear optical crystals KBBF with a multi-layer structure can realize outputs of an ultraviolet laser and a deep ultraviolet laser with high efficiency and high power.