In　this　paper,　the　method　of　recognition　and　superposition　of　sub-pixel　shifting　in　digital　holograms　is　investigated.　A　group　of　non-scanning　holograms　is　recognized　and　superposed　by　using　sub-pixel　shifting　algorithm.　Further,　spatio-temporal　scanning　holograms　with　sub-pixel　displacement　are　recognized　and　superposed　to　further　improve　imaging　resolution　by　combining　spatio-temporal　scanning　digital　holography　with　sub-pixel　shifting　algorithm.　The　experimental　results　verify　the　feasibility　of　improving　resolution　with　sub-pixel　displacement.