The present invention relates to a fibrinolysin gene of Agkistrodon acutus, a vector containing the said gene and the host cell which transformed by the vector. The fibrinolysin could be used in treating diseases caused by thrombus. The fibrinolysin FII is purified from the crude venom of Agkistrodon acutus, and the corresponding gene is cloned. It is recommended to produce the fibrionolysin by the yeast expression system. The activity of the fibrionlysin is also determined. The advantages of this invention are that the expression level and activity of the fibrinolysin are both high and the quality of the fibrinolysin is stable.