This review article highlights atom-level control of the heterojunction and homojunction in SnO2-TiO2 nanohybrids, and the effects on the photocatalytic property. Firstly, a comprehensive description about the origin for the SnO2-TiO2 coupling effect on the photocatalytic activity in the conventional SnO2-TiO2 system without heteroepitaxial junction is provided. Recently, a bundle of thin SnO2 nanorods was hetero-epitaxially grown from rutile TiO2 seed nanocrystals (SnO2-NR#TiO2, # denotes heteroepitaxial junction). Secondly, the heterojunction effects of the SnO2-NR#TiO2 system on the photocatalytic activity are dealt with. A novel nanoscale band engineering through the atom-level control of the heterojunction between SnO2 and TiO2 is presented for the photocatalytic activity enhancement. Thirdly, the homojunction effects of the SnO2 nanorods on the photocatalytic activity of the SnO2-NR#TiO2 system and some other homojunction systems are discussed. Finally, we summarize the conclusions with the possible future subjects and prospects.