Abstract: To make the classification of Helminthism of the livestock and poultry more convenient and short-cuting, the key system was set up by the programming language of Visual Basic. According to the morphologic characters of the orders, families and genuses of Cestoidea, Trematoda and Nematoda, a database was established. The correlative data can be searched easily and quickly. And the key system was set up by simulating the steps of morphologic classification and index, on the basis of the bidirectional index of parasite names and morphology. The system has very practical values in the works of epidemic disease preventing and curing on livestock and poultry, health and quarantine of public, health and quarantine of food, custom quarantine of imports and exports ,the market testing.