In the production process of recombinant protein, in order to facilitate the expression, detection, tracer and purification of the target protein, a polypeptide or protein is usually fused with the target protein by using DNA in vitro recombination technology, which is called protein tag. Commonly used protein labels include His label, Flag label, HA label, c-Myc label, GST label, GFP label and so on. Antibodies that recognize the label are called tag antibodies, and tag antibodies can be used to detect or purify the tag sequence on the expression vector to study the expression level and function of the target protein.