By introducing MoO2–C nanomaterials into Mn0·2Cd0·8S nanorods, the S-scheme heterojunction of MoO2–C/Mn0·2Cd0·8S with unique interface microstructure was successfully constructed. It is worth mentioning that there is a disorder region in MoO2–C nanocomposites, which provides the main active center for photocatalytic decomposition of water. Photoelectrochemical tests show that the existence of S-scheme heterojunction and carbon rod leads to the rapid separation of charge and the effectively decrease of hydrogen evolution potential. S-scheme heterojunction can promote the charge separation and transfer between MoO2–C and Mn0·2Cd0·8S quickly and effectively. Compared with pure Mn0·2Cd0·8S, MOCMCS has high hydrogen evolution activity, and its activity is about 13 times higher. The significant improvement of photocatalytic performance is due to the existence of S-scheme heterostructure between MoO2–C/MCS and small transfer resistance, coupled with the excellent conductivity of carbon rods, which effectively promote the charge separation and transfer between MoO2–C and Mn0·2Cd0·8S nanorods. •There is a disorder zone on the interface between carbon material and MoO2 crystal plane.•S-scheme heterojunction composed of MoO2–C and Mn0·2Cd0·8S was formed.•The presence of carbon rods greatly inhibits the recombination of photogenerated electron-hole pairs.