Based on the SnS2 and Janus-PtSSe monolayers, we designed six new vdW heterostructures (HS). By investigating their structural stability, we selected out the structure most likely to be synthesized in the experiment, AA-stacking SnS2/SPtSe HS. Then we further explored its electronic, optical and photocatalytic properties, and found that this HS has a suitable band gap and considerable optical absorption coefficient. In addition, the HS possesses a typical type-II band structure and build-in electric field from SnS2 to SPtSe at the interfaces, which is benefit to separate the carries into different spaces to enhance its catalytic properties. At the end of this work, photocatalytic properties of this HS for water splitting were studied. Appropriate band edges for SnS2/SPtSe HS make it as potential photocatalyst for water splitting in acid environment.