This invention provides a fusion protein (FP4) and the code gene, expression method, and clinical application; its goal is to provide a fusion protein, the code gene, and the expression method as well as to take this fusion protein as the active constituent anti-allergic medicine. In addition, the invention provides the sequence of fusion protein attached on SEQ ID 2 and any derivation protein of the fusion protein (FP4) which includes adding or deleting several amino acids of SEQ ID2 as well as increasing or deducing nuclear tides of SEQ ID 1. We designed to cross-link IgE active receptor and an IgG inhibitory receptor by endogens hinge without any extraneous chemical link. This invention fusion protein has function to block the IgE acceptor, moreover fragment of fusion protein has ability to specifically bind to a native IgG inhibitory receptor containing immunoreceptor tyrosine-based inhibitory motif, thereby inhibiting the IgE-driven mediator release from mast cells and basophils. It will play important role in the allergic disease treatment.