The invention relates to a method for manufacturing a double-layer film of a crystalline silicon solar cell. The method is characterized by comprising the following specific steps of: mixing tetraethyl orthosilicate and ethanol, stirring and heating, adding dilute solution of hydrochloric acid into the solution, cooling, adding an organic additive into the solution, stirring and dissolving, and closing and aging to obtain a sol; and preparing a substrate of the crystalline silicon solar cell by a routine method, forming a silicon nitride film by a plasma enhanced chemical vapor deposition method, spraying the prepared sol on the silicon nitride film to prepare a silicon dioxide film, performing heat treatment on the obtained silicon dioxide film at the temperature of between 200 and 600 DEG C, printing positive and negative electrodes and a back field, drying, and sintering. The method has the advantages that: the light reflectivity of the surface of the solar cell is lower; the power of a solar cell plate is higher; and the short-wave and long-wave absorption of the double-layer film cell is further improved.