Abstract: ObjectiveEffects of different immunization times on FMDV antibodies from pigs in intensive pig farms were studied to provide references for FMDV immunization. MethodTaking 100 sows as a boundary, 720 pig serum samples were collected from 16 farms. These serum samples had been collected after one month of prime, first boost and second boost for FMD vaccination, respectively. The antibody levels of these serum samples were measured by blocking-ELISA technique.ResultThe ratio of antibody positive of prime, first boost and second boost for FMD was 52.08%,72.08%and 86.67%, and dispersion was 53.83%,75.75%and 106.46%. S/N level was 0.527, 0.387 and 0.294, respectively. The ratio of antibody positive of prime and second boost and S/N level were extremely significantly different (P<0.01). The ratio of antibody positive of prime and second boost and dispersion were significantly different (P<0.05). Average antibody positive ratio, dispersion and S/N of those farms with more than 100 sows was 75.83%, 87.71%and 0.350, while for farms with less than 100 sows, average anti-body positive ratio, dispersion and S/N was 64.72%, 67.47%and 0.455, respectively. There was extremely significant differ-ence (P<0.01) between FMD antibody levels and S/N value from different scales of farms, but there was no significant differ-ence between FMD antibody levels and dispersion (P>0.05). ConclusionThe prime immunization could not meet national standards. The second boost immunization showed the best antibody levels. In practical operation, intensive pig farms should enhance the monitoring of FMDV antibodies, optimize the vaccination procedures based on the results of antibody monitoring and improve antibody uniformity in different herds of pigs to effectively control and prevent FMD prevalence.