The invention provides a rupatadine fumarate compound which has dual effects of antihistamine and antagonistic platelet activating factor (PAF). According to the research, allergy and inflammatory diseases are multi-factor complex processes caused by generation and release of various different media; histamine is the most inflammatory medium appearing in allergy early symptom, and the disease symptoms including sneezing, rhinocnesmus, tearing, running nose, skin itch, wheal and the like are mostly caused by histamine H1 receptor. And PAF also can cause bronchial constriction and increased permeability of the vessel, so that running nose, nasal congestion, wheal and itch are caused; meanwhile, the PAF is also a main cause of asthma. The antiallergic drug which is clinically used only has an antihistamine activity effect, but does not have a PAF antagonistic effect.