The invention discloses a solar cell in a bi-component gradual change structure, and a preparation method for the solar cell. The solar cell comprises a substrate, a bottom electrode contact layer, a bottom component gradual change layer, an absorption enhancement layer, a top component gradual change layer, a top electrode contact layer, a top electrode, a bottom electrode, and a passivation layer. The bottom electrode contact layer grows on the substrate. The bottom component gradual change layer, the absorption enhancement layer, the top component gradual change layer, the top electrode contact layer and the top electrode are sequentially disposed on a part of the bottom electrode contact layer. The bottom electrode is disposed on a part of the bottom electrode contact layer. The passivation layer covers the side surfaces of all layers, and the top component gradual change layer can absorb all solar spectrums to some degree and can effectively improve the photoelectric conversion efficiency. A part of sunlight passing through the top component gradual change layer can be further absorbed by the absorption enhancement layer. The bottom component gradual change layer can eliminate an electronic (hole) conveying barrier, and can adjust and control crystal lattice stress, so as to improve the growing quality of materials.