Abstract: To explore the synergisic effect of DH (Dendrobium huoshanense) and KBT (Keemun black tea) on preventing immunity reduction. The solid-liquid ratio, extraction time and extraction times of DH and KBT were studied by single factor test and orthogonal test with the extraction rate of Dendrobium polysaccharide and black tea polyphenols as indexes, the extraction techniques of DH and Keemun black tea were optimized respectively. The optimal ratio of KBT and DH was determined by toxicity test and phagocytosis test on RAW264.7 cells. The results showed that the optimum extraction conditions of DH polysaccharide were as follows: The ratio of material to liquid was 1:80 (g/mL), the extraction time was 80 min, and the extraction times were 4 times. The optimum extraction conditions of KBT polyphenols were as follows: The ratio of material to liquid was 1:80 (g/mL), the extraction time was 25 min, and the extraction times were 5 times. The ratio of KBT to DH was determined by observing the effect of different proportions of the mixture on macrophages. The results of the in vitro experiment showed that the extract mixture of 75% KBT and 25% DH had the best immune-enhancing effect. The results of the in vivo test showed that the high-dose group of KTDH could significantly reduce the changes of levels of cytokines IL-2 and IL-6 due to immunosuppression in mice (P<0.01). To sum up, DH and KBT can synergistically enhance immunity and prevent immune decline, which can provide new ideas for the development and application of DH and KBT.