NOVELTY - The method comprises soaking a glass substrate into diluted hydrochloric acid, ultrasonically oscillating the substrate for 30-60 minutes, washing the substrate for three times using distilled water, placing the substrate into mixed solution of concentrated sulfuric acid, hydrogen peroxide and deionized water for 24-72 hours, washing the substrate using distilled water and absolute ethanol using nitrogen, where the weight ratio of sulfuric acid, hydrogen peroxide and deionized water is 1:1:1, and adding pure soluble copper salt into deionized water to prepare transparent solution.    USE - The method is useful for preparing x-shaped flaky crystal cross structure copper sulfide thin film, which is useful in a light-emitting device, a thermocouple, a filter, a solar energy battery, a sensor and a catalyst.    ADVANTAGE - The method provides the x-shaped crystal structure copper sulfide thin film with compact structure, good repeatability, high crystallinity, excellent conductivity and improved electrical and optical properties under short reaction cycle and low reaction temperature in environment-friendly, cost-effective and simple manner.    DETAILED DESCRIPTION - The method comprises soaking a glass substrate into a diluted hydrochloric acid, ultrasonically oscillating the substrate for 30-60 minutes, washing the substrate for three times using distilled water, placing the substrate into mixed solution of concentrated sulfuric acid, hydrogen peroxide and deionized water for 24-72 hours, washing the substrate using distilled water and absolute ethanol using nitrogen, where the weight ratio of sulfuric acid, hydrogen peroxide and deionized water is 1:1:1, adding pure soluble copper salt into deionized water to prepare transparent solution with 0.003-0.1 mol/l of cupric ion, adding EDTA to obtain a solution A, where the ratio of the cupric ion and the EDTA is (5-10):1, adding thiourea or methylamine into the solution A to obtain a solution B, where the thiourea or methylamine has a concentration of 0.006-1.0 mol/l, adding ammonia monohydrate into the solution B, adjusting a pH value to 5-7 to prepare a precursor solution C, pouring the precursor solution C into a microwave hydrothermal reaction kettle with a filling degree of 50-80%, vertically placing the glass substrate into the reaction kettle, sealing the reaction kettle at a temperature of 100-150 degrees C for 30-90 minutes, cooling the glass substrate to room temperature after the reaction is finished, opening the reaction kettle, taking out the substrate, transferring 0.5-2 mol/l of sodium hydroxide solution into the reaction kettle, sealing the reaction kettle to perform secondary crystallization at a temperature of 100-150 degrees C for 1-2 hours, naturally cooling to the room temperature after the reaction is finished, taking out the substrate, vacuum drying the substrate at a temperature of 40 degrees C to obtain a x-shaped flaky crystal cross structure copper sulfide thin film.