The invention relates to a method for preparing a colorful film for protecting a solar cell thin grid line metal electrode by adopting a mask. In the method, after a solar cell is prepared, a mask is utilized to cover a main grid line metal electrode on the front surface of the solar cell, a film is coated on the area which is not covered by the mask for the second time, and a dielectric layer for protecting the thin grid line metal electrode is prepared to form a structure comprising the dielectric layer, the thin grid line metal electrode and a passivation layer. The method can protect the thin grid line metal electrode against easy oxidation, and the main grid line metal electrode can be normally connected by welding rods. The passivation effect of the front surface can be enhanced through optimizing the passivation layer; the reflectivity of the front surface of the solar cell can be reduced and color regulation can be realized through regulating the dielectric layer; and characters, figures, graphics and the like can be displayed on the front surface of the solar cell through changing a mask pattern. In addition, the secondary film coating method is convenient to be in butt joint with the traditional crystalline silicon solar cell preparation process and is easy for industrialization.