Abstract: A novel thrombin inhibitor was identified and purified from salivary glands of ixodid tick,Ixodide sinesis by gel filtration and RP-HPLC. The molecular weight was 6.356 kDa determined by MALDI-TOF mass spectra. It was different from any known serine protease inhibitors identified from ixodid ticks. This inhibitor inhibited thrombin with strong potency,and exhibited no obvious effects on factor Xa and trypsin. The thrombin inhibitor may be used as a candidate to develop vaccine to control ticks.