The invention provides an NK cell in-vitro amplification system. The NK cell in-vitro amplification system comprises an activation culture medium for cell activation and a proliferation culture medium for cell proliferation, the activating culture medium is composed of an activating agent and a basic culture medium, and the activating agent is a combination of solid-phase anti-CD52 and IL-2; the proliferation culture medium is composed of a proliferation agent and a basic culture medium, and the proliferation agent is IL-2. Compared with the prior art, the NK cell in-vitro amplification system disclosed by the invention has the following technical effects: 1) the culture medium contains the immobilized anti-CD52, and the NK cells can be efficiently stimulated to enter an activated and proliferated state by combining the use of IL-2, so that a large number of activated NK cells can be easily obtained; moreover, no trophoblasts are used in the culture process, and the prepared NK cells can be used for clinical research and treatment; and 2) the NK cell culture method is simplified, few NK cell activation components are used, few material resources and manpower are used, the production cost of NK cell preparation is obviously reduced, and the method is particularly suitable for large-scale production.