Due to the difference of the Classical Swine Fever epidemic，the Classical Swine Fever immunization program according with local is one of key measures for effective prevention and control of the Classical Swine Fever. In the immunization program research，determination of the most fit age for first immunization and immune dosage are two important objects. This paper uses PPA（enzyme staphylococcal protein A）- ELISA method to make monitoring experimental research into maternal antibody and immune antibody of the Classical Swine Fever a pig farm of Daxian. The experiment shows that 25 days is the most fit immunization age，1 times dosage for the most fit immune dosage.