Kesterite structure semiconductor Cu 2 ZnSn(S,Se) 4 is one of the most promising candidate as a light absorber material to overtake the next generation of thin film solar cells, owing to its low cost, non-toxic, and earth abundant source materials. The Shockley-Queisser limit of the single junction Cu 2 ZnSn(S,Se) 4 solar cell is over 30%, signifying a large potential of this family of solar cells. In the past years, with the development of synthesis techniques, Cu 2 ZnSn(S,Se) 4 solar cells have attracted considerable attention and the power conversion efficiency of Cu 2 ZnSn(S,Se) 4 solar cell has experienced a rapid progress. Presently, the certified champion efficiency of CZTSSe solar cells has reached to 12.6%, which is far below the efficiency of Cu(In,Ga)Se 2 solar cell. In this review, the developments of Cu 2 ZnSn(S,Se) 4 solar cells in recent years are briefly reviewed. Then the fundamental understanding of Cu 2 ZnSn(S,Se) 4 solar cells is introduced, including materials and device structure, as well as the band alignment of hetero-junction and their impacts on device performance. After that, we mainly review the progress and achievements in the preparation processes, through vacuum and non-vacuum based processes. Finally, we outline the challenges and perspectives of this promising solar cell.