The invention discloses a device and a method for detecting an orbital angular momentum of a light field. The device consists of an ultra-sensitive holographic surface set, a coupling grating, a silicon dioxide substrate and silicon detectors. By the method, a holographic function is integrated on a metal micro-nano structure to form ultra-sensitive holographic surfaces. Each holographic surface has a plurality of regions with different topological charges, a to-be-detected vortex light field with a radial polarized component can be coupled into a plurality of surface plasma wave focusing fields, and spreading directions of the surface plasma wave focusing fields depend on a total angular momentum of a system. After being transmitted by the coupling grating, focusing surface plasma waves generated in various regions of each holographic surface can be collected by the silicon detectors. Signals of the detectors are quantified, and large-range high-fidelity recognition on the orbital angular momentum of the light field can be implemented. Compared with the traditional method for detecting an orbital angular momentum of a light field, the method for detecting the orbital angular momentum of the light field has the advantages of microminiaturization, easiness in integration, large detection range, real-time detection capability and the like. The device and the method for detecting the orbital angular momentum of the light field can be applied to various fields of light communication and information processing.