The invention relates to a solution and method for one-step electrodeposition of a Cu2ZnSnS4 (CZTS) prefabricated layer film, and belongs to the technical field of CZTS films. The solution for one-step electrodeposition of the CZTS prefabricated layer film comprises 0.001-0.005 mol/L of metal salt, 0.03-0.1 mol/L of thiosulfate, 0.1-0.4 mol/L of conducting salt, 0.01-0.5 mol/L of hydroxy acid, 0.01-0.5 mol/L of thiourea derivative and 1-5 g/L of stabilizer, wherein the pH value of the solution is 1-6.0. The method for one-step electrodeposition of the CZTS prefabricated layer film includes the steps that (1) the solution for preparing the CZTS prefabricated layer film is placed in a plating bath; (2) a three-electrode system is used for connecting a power controller, a reference electrode, a conducting substrate and an inertia anode, and a salt bridge is used for connecting a reference electrode solution and an electrodeposition solution; (3) a power supply is on, and a constant potential method is used for conducting codeposition on Cu, Zn, Sn and S; and (4) the deposited CZTS prefabricated layer film is taken out, washed and dried. The solution and method are simple and practical, stable in solution system, simple in technology, easy to operate, safe, environmentally friendly and suitable for large-area preparation of the CZTS films.