NOVELTY - Preparing copper indium selenide flexible thin film solar cell light absorption layer comprises removing oil from the polyimide thin film, and impregnating the polyimide film into the acetone, and washing; roughening the polyimide thin film and oil; activating the two thick polyimide films after putting in the activating liquid to activate ultrasonic additive impregnation, activating the polyimide dipping film, heat treatment; and applying reduced polyimide film into chemical plating solution, and depositing the polyimide film on the surface copper indium selenide.    USE - Method for preparing CIS flexible thin film solar cell light absorption layer.    DETAILED DESCRIPTION - Preparing copper indium selenide (CIS) flexible thin film solar cell light absorption layer comprises:    (A) removing oil from the polyimide thin film, and impregnating the polyimide film into the acetone for 5 minutes, and then sequentially using washing powder water, tap water and distilled water to wash to the surface without stringing;    (B) roughening the polyimide thin film and oil, coarsening the polyimide film into a liquid for 10-20 minutes, putting sodium hydroxide (NaOH) solution in liquid, where the NaOH solution is at 80-90 degrees C, and the concentration is 10-50 g/L;    (C) putting the two thick polyimide films after putting in the activating liquid to activate ultrasonic additive impregnation for 30-40 minutes, carrying out at 200-230 degrees C to activate the polyimide dipping film, heat treatment for 30-40 minutes, where the activating solution is present at 50 g/L, the concentration of sodium hypophosphite is 50-60 g/l, the concentration of the nickel sulfate is 40-50 g/l and the concentration of the sodium hydroxide is 20-30 g/l, adding the sodium hypophosphite, nickel sulfate and sodium citrate into water to mix uniformly;    (D) repeating the step three times each;    (E) after the activation heat treatment of the polyimide film into sodium hypophosphite solution, until a polyimide film surface all the metal luster is stopped, the 20-30 g/L sodium hypophosphite solution is at 100 degrees C;    (F) applying reduced polyimide film into chemical plating solution for 30 minutes, where the chemical plating solution is present at 30-40 g/l, the concentration of the sodium phosphate is 25-30 g/l, the concentration of nickel sulfate is 10-15 g/l, the concentration of the sodium citrate is 10-15 g/l and the concentration the sodium acetate is 10-15 g/l, adding the sodium hypophosphite, nickel sulfate, sodium citrate and sodium acetate into water to mix uniformly; the pH of the chemical plating solution is 4.5-5 and the temperature is 85-95 degrees C; and    (G) using electrodeposition method to deposit the polyimide film on the surface CIS, where the surface CIS of the polyimide thin film is light absorbing layer of CIS flexible thin film solar cell.