The invention belongs to a flexible CIGS thin-film solar cell and a process for preparing an absorption layer thereof, the flexible CIGS thin-film solar cell is a multi-layer film structure, which comprises an substrate, a bottom electrode, an absorption layer, a buffer layer, a window layer, an anti-reflecting film and an upper electrode, and the flexible CIGS thin-film solar cell is characterized in that the substrate is made of flexible metals or polyimide. The process for preparing the adsorption layer of the flexible CIGS thin-film solar cell is characterized in that the substrate is made of flexible metals or polyimide, the bottom electrode Mo of the thickness of 0.5-1.5 mu m is deposited by magnetron sputtering, a metal prefabricating layer is prepared on a Mo thin-film, and is in vacuum seal to be placed in a furnace to heat, the temperature of the area of a solid selenium source is controlled between 180-300 DEG C to perform selenizing treatment, thereby enabling the metal prefabricating layer to be transformed into a semiconductor thin-film. Through performing selenizing or vulcanizing under saturation vapor pressure of selenium or sulfur in a vacuum seal silica tube, controllable repeatability of the technique process is fine, use quantity of selenium or sulfur is reduced, besides, the process is controllable and the equipment is simple.