The invention discloses a rigid-flexible combined printed circuit board preparation method. The rigid-flexible combined printed circuit board comprises a rigid sub board, a dielectric layer, a flexible sub board, another dielectric layer, and another rigid sub board which are laminated sequentially. The method comprises the following steps of: flexible board preparation, rigid board preparation, dielectric layer preparation, pressing, cover opening, and post processes. In the invention, a PI film resistance glue is pasted in a rigid board slot area; a flow type prepreg (a PP sheet) windowing area is increased; and the total thickness of the PP sheet is controlled to be less than the total thickness of a polyimide cover film and a polyimide resistance glue film, so that the flow type prepreg can be applied to preparation of the rigid-flexible combined printed circuit board. The excessive glue length of the rigid-flexible connecting point of the pressed printed circuit board is less than 1.0mm, so that the requirements of the IPC-6013B relevant regulation are met.