Abstract: The aim of this study was to provide scientific data for establishment of better vaccination procedures in chicken breeders or layers. Different statistic designs and analysis were compared to follow dynamic changes of antibody titers to Newcastle disease virus，H5 and H9 avian influenza viruses in a chicken breeder farm of large scale. It was indicated that the statistic design and analysis by ttest for paired comparisons could prevent some false decreases in antibody titers caused by technical or systemic errors and easily detect the small but real decrease in antibody titers, such small decrease may be covered by big standard deviations due to individual variances if test for comparison between two sample means was used. The statistic design and analysis by ttest for paired comparisons made conclusions more convenient and reliable than that by ttest for comparison between two sample means in determination of real decreases in antibody titers to Newcastle disease virus, H5 and H9 avian influenza viruses.