Although the water gas shift (WGS) reaction has sparked intensive attention for the production of high-purity hydrogen, the design of cost-efficient catalysts with noble metal-like performance still remains a great challenge. Here, we successfully overcome this obstacle by using Se-incorporated MoS with a 1T phase. Combining the optimized electronic structure, additional active sites from edge sites, and a sulfur vacancy based on the 1T phase, as well as the high surface ratio from the highly open structure, the optimal MoSSe exhibits superior activity and stability compared to the conventional 2H-phase MoS, with poor activity, large sulfur loss, and rapid inactivation. The hydrogen production of MoSSe is 942 μmol, which is 1.9 times higher than MoS (504 μmol) and 2.8 times higher than MoSe (337 μmol). Furthermore, due to the lattice stabilization Se-incorporation, MoSSe exhibited excellent long-term stability without obvious change in more than 10 reaction rounds. Our results demonstrate a pathway to design efficient and cost-efficient catalysts for WGS.