The present invention provides a venene haemocoagulase gene and its expression for the functional protein. The haemocoagulase gene of the present invention has a nucleotide sequence shown by the sequence list SEQ ID NO: 1 or the mutated nucleotide sequence formed by replacement, depletion, or addition of one or more nucleotide based on the said nucleotide sequence with an equivalent function. The said haemocoagulase has amino acid sequence shown by SEQ ID NO: 2. Haemocoagulase of the present invention has an obvious hemostatic effect, a broad effective dose range, safe and reliable application, which creates good conditions for the development of genetic engineering products of recombinant haemocoagulase in the future.