The transfer/separation of interfacial charge carriers relies heavily on the appropriate interfacial contact of heterojunction. In-situ heterojunction will be an effective way for enhancing charge transfer rate since the tight interface, which is conductive to promote the photoelectrochemical or photochemical activity. Herein, 0D/2D SnO2/SnS2 novel Step-scheme (S-scheme) heterojunctions have been successfully constructed by solvothermal method and in-situ oxidation technique through controlling the annealed temperature in N-2/H-2 atmosphere. The SnS2 nanosheets annealed at 400 degrees C (SS-400) reveals the highest photocurrent density (0.33 mA cm(-2)) at 1.23 V vs. RHE under AM 1.5G, that is approximately of 1.9 and 1.2 times than SS-300 (0.17 mA cm(-2)) and SS-500 (0.27 mA cm(-2)), respectively. The SS-400 shows the hydrogen and oxygen evolution of 5.5 and 2.7 mu mol cm(-2) h(-1), and the corresponding faradaic efficiencies are about 89.4% and 87.7%, respectively. The mainly enhanced reason of SS-400 is that appropriate amount of 0D SnO2 nanoparticles generated on the surfaces and edges of 2D SnS2 nanosheets fabricate the in-situ of S-scheme heterojunctions, which are accelerating the recombination of carriers with relatively weaker redox capacity and promoting the separation of carriers with relatively stronger redox capacity. Meantime, the barrier factor, internal electric field, coulomb interaction, and applied bias factors can also promote the recombination of carriers with weak redox capacity (electrons of SnO2 and holes of SnS2). This work will provide a novel thought for designing and constructing the mechanism of S-scheme heterojunctions for photoelectrochemical water splitting.