A unit for preparing groups (1) of products in layers (S) for palletizing comprises: a motor-driven element (4) for controlled pick up and release of the groups (1) of products from the first surface (3) to a second surface (5), positioned by the side of the first surface (3), for preparing a layer (S) of groups (1) of products; a logic unit (7) for controlling and programming the pick up and release element (4) and the second surface (5) to obtain individual layers (S) made up of two or more groups (1) of products on the second surface (5) by moving them along or around axes, transversal (Y) to the extension of the first surface (3), parallel (X) with the extension of the first surface (3), at a vertical height (Z) and according to an angle (α) of rotation about the vertical axis (Z); the pick up and release element (4) having independent drive units (9, 10, 11) designed to control the element (4) according to three of the controlled axes (X, Y, Z, α); the second preparation surface (5) having a drive unit (12) for controlling the second surface (5) along the remaining controlled axis (X, Y, Z, α) to place the groups (1) of products so as to form the layer (S), with an interface unit (13) inserted between the logic unit (7) and the element (4) and second surface (5), allowing the four axes (X, Y, Z, α) to be coordinated in such a way as to form the layer (S).