We demonstrate a simple approach to fabricate Cu2ZnSn(S, Se)(4) (CZTSSe) absorber with increased-sulfur content surface. It is well known that the problem of interface recombination in CZTSSe solar cells is the issue for further improving efficiency. The beneficial effects of surface sulfurization were reported in Cu(In, Ga)(S, Se)(2) solar cells. However, very limited works have been reported on the effects of surface sulfurization on CZTSSe solar cells, which is a critical factor to improve the surface and achieve higher efficiency. In this work, we fabricate the CZTSSe absorber by selenizing the sulfur-containing stacked precursors. The sulfur-modified surface is achieved by introducing H2S gas during cooling stage of the selenization process. The effects of surface sulfurization on composition, structure, morphology, and electric properties of CZTSSe are thoroughly investigated. The open circuit voltage can be increased significantly from 312 mV (without H2S) to 400 mV (with H2S) due to the increment of front surface bandgap and reduction of interface recombination. Surface localized electric properties are improved, and interface defect density is decreased due to surface passivation by using H2S gas. The efficiency of CZTSSe solar cell substantially increases from 5.01% (without H2S) to 7.38% (with H2S). The proposed approach can be easily applied to various CZTSSe processes to passivate the surface and form larger surface bandgap, leading to lower interface recombination, which paves a new avenue to further improve the CZTSSe efficiency.