The invention relates to a method and device for deep oil removal of wastewater containing low-concentration sump oil. The method comprises the following steps: allowing the wastewater containing the low-concentration sump oil to enter the device through an inlet, firstly uniformly distributing a fluid by use of a flow regulator, secondly capturing trace of oil droplets through a knitted layer formed by an oleophylic and hydrophobic fiber knitted layer and a hydrophilic and oleophobic knitted layer which are knitted in a certain manner, demulsifying and separating trace of agglomerated and grown oil-in-water emulsion, and finally realizing rapid agglomeration, growing and separation in a corrugation enhancement and settling separation manner. The invention also provides a set of device for implementing the method. The device comprises a plurality of parts including a shell, a feeding pipe, the flow regulator, a fiber agglomerated layer, a corrugation enhanced separating layer, a liquid level meter and the like. The technique is high in separation efficiency, small in energy consumption, long in continuous running period and widely applicable to a treatment process of each wastewater containing the low-concentration sump oil.