A manufacturing method for an IGZO active layer is disclosed. The method comprises steps of: after depositing a first metal layer and a gate insulation layer on a substrate, depositing an IGZO material on the gate insulation layer, and forming an IGZO film; and performing a plasma cleaning treatment on a surface of the IGZO film by using an argon gas or a helium gas to adjust element contents on the surface of the IGZO film, and forming an IGZO active layer. The present invention also correspondingly discloses a manufacturing method for an oxide thin film transistor. By implementing the embodiments of the present invention, the elements on the film surface of the IGZO active layer can be adjusted to improve electrical properties.