The invention belongs to the technical field of chemical medicines, and relates to a bridge ring piperazine derivative or salt thereof, a preparing method of the derivative and application of the bridge ring piperazine derivative or salt thereof in preparing medicines for treating ROR gamma t related diseases. Through experiments, the result shows that the bridge ring piperazine derivative can effectively restrain ROR gamma t protein receptors, adjust the differentiation of Th17 cells and restrain the generation of IL-17, can further be used as the treatment medicines for treating the ROR gamma t mediated inflammation related diseases and is particularly suitable for treating the inflammation related diseases such as disseminated sclerosis, rheumatoid arthritis, collagen induced arthritis,psoriasis, inflammatory bowel disease, encephalomyelitis, cloning diseases, asthma and cancers. The chemical formula can be seen in the description.