Horseflies are economically important blood-feeding arthropods and also nuisance for humans, and vectors for filariasis. They rely heavily on pharmacological propriety of their saliva to get blood meal and suppress immune reactions of hosts. Little information is available on antihaemostatic substances in horsefly salivary glands; especially no horsefly immune suppressants have been reported. By proteomics or peptidomics and transcriptome analysis coupling with pharmacological testing, several families of proteins or peptides, which act mainly on haemostatic system or immune system of the host, have been identified and characterized from 30, 000 pairs salivary glands of the horsefly of Tabanus Yao (Diptera, Tabanidae). They are: () a novel family of inhibitors of platelet aggregation including two members, which possibly inhibit platelet aggregation by a novel mechanism and act on platelet membrane, () a novel family of immunosuppressant peptides including twelve members, which can inhibit interferon- production and increase interleukin-10 secretion, () a serine protease inhibitor with 56 amino acid residues containing anticoagulant activity, () a serine protease with anticoagulant activity, () a protease with fibrinogenolytic activity, () three families of antimicrobial peptides including six members, () a hyaluronidase, () a vasodilator peptide, which is a isoform of vasotab identified from Hybomitra bimaculata, () interestingly, two metallothioneins, which are the first report of metallothioneins from invertebrate salivary glands. The current works will facilitate to understand the molecular mechanisms of the ectoparasite-host relationship, and help in identifying novel vaccine targets and novel leading pharmacological compounds.