The present application provides a solar cell and a preparation method thereof. The method includes: forming a target amorphous silicon layer on a side of a silicon wafer using a preset process, and then performing an annealing treatment on the target amorphous silicon layer to convert the target amorphous silicon layer into a target polycrystalline silicon layer, wherein the preset process includes at least one cycle period, the at least one cycle period comprises: depositing a target amorphous silicon preformed layer with a preset thickness and performing a hydrogen gas plasma treatment on the target amorphous silicon preformed layer, wherein the preset thickness of the target amorphous silicon preformed layer is less than or equal to a thickness of the target amorphous silicon layer. This method can effectively improve a crystallization rate of converting amorphous silicon into polycrystalline silicon, improving field passivation performance and contact performance of the solar cell.