Fully-humanized anti-human interleukin 17a single-chain antibody

The invention discloses a fully-humanized anti-human interleukin 17A single-chain antibody, relates to the technical field of genetically engineered antibodies and specifically relates to a fully-humanized antibody fragment which is genetically engineered, screened, expressed and provided with special affinity with interleukin 17A (IL-17A). The genetically engineered antibody fragment is connected with a heavy chain region and a light chain region end to end by virtue of a soft connecting fragment. By constructing a great-capacity natural phage antibody library, an antibody fragment with special adsorption capacity on IL-17A is obtained by biological elutriation. The antibody fragment is constructed into a full-length antibody, so that the reaction of IL-17A on interleukin 6(IL-6) released by a human fibrosarcoma cell HT1080 can be inhibited by virtue of eukaryotic secretory expression and affinity purification. The antibody fragment disclosed by the invention can be used for detecting and treating rheumatoid arthritis.