Abstract: Objective：To study the pathogenicity of Ureaplasma urealyticum serotype 3（Uu3） and 8（Uu8） with the same concentration in Female Rabbits，s Reproductive tract. Methods：Fifty-two oestradiol-treated adult female rabbits were randomly divided into group A，B，C and D. Ureaplasma urealyticum serotype 3，8，3 and 8，with the same concentration of 106copy/g while 4 rabbits of control group（group D） inoculated sterile medium.They were detect Uu from cervical secretions by fluorescent quantitative polymerase chain reaction（FQ-PCR） at 1，3，7， 14， 21， 35，49，63，77，91，105 days. They were necropsied at 14，105 days of postinoculation randomly to observing tissues of cervix，endometria，fallopian tube by light microscope and cervical mucosa by scanning electron microscope. Results：①The total positive rabbits of Uu in three experimental groups show a significant difference（P＜0.05），which were 27.3%（25/88），55.7%（49/88），69.3%（61/88）. But before 35 days，the positive rate of the three experimental groups at the same time point in all of Female rabbits infected cervical secretions does not show a statistically significance（P＞0.05），and the positive rate descended as the days of postinoculation lasting. The highest positive rates of three experimental groups were 87.5%（7/8），100.0%（8/8），100.0%（8/8） at 1 d after inoculation，but the conlisation didn't persist at 105 d. All rabbits of control group were negative. ②There was not statistical difference in the quantity of Uu among experimental groups（P＞0.05）. Their peak level were 364×104copy/g，401×104copy/g，493×104copy/g，reached at 1d，but the FQ-PCR values reduced as the days of postinoculation lasting.In the same experimental group at different time points，the concentrations was a significant difference（P＜0.05）.③The total pathogenicity rates of three groups were significantly different（P=0.015），which were 31.3%（5/16），62.5%（10/16），81.3%（13/16）. But there were not statistical difference among experimental groups at 14 days（P＞0.05），but 105 days later the pathogenicity rates of three groups were significant different（P=0.041）. None of control group was positive. Conclusions：①In female rabbits′s reproductive tract，the pathogenicity of each experimental group was shown when inoculatin Uu with FQ-PCR value is 106copy/g. the pathogenicity rates of three groups were significantly different. the pathogenicity of the mixed group（group C） was the highest and Uu3 group（group A） the lowest，Uu8 group（groupB） was the Second. ②In Female Rabbits，s Reproductive tract，the infectivity and quantatitive value were significant different among experimental groups，the infectivity and quantatitive value of the mixed group （group C） was the highest and Uu3 group（group A） the lowest，Uu8 group（group B） was the Second when inoculating Uu with the same concentration. ③The pathogenic concentration of Uu3 and Uu8 may differ，Uu8 may be ＜106copy/g，so further research is needed confirm it.

Key words: Ureaplasma urealyticum, Serotyping, Polymerase chain reaction, Virulence, Models, animal