[目的]分析2018—2022年23 个省份381 个规模奶牛场成母牛乳房炎发病事件,主要影响乳房炎的可能因素：发病月份、发病乳区位置和个数、发病次数、产后天数、胎次、严重程度等。[方法]每头牛同一胎次内不同产后天数多次发病记为多次。发病次数统计根据所有牛只乳房炎事件进行计数求和,不同因素下各水平占比根据各水平乳房炎计数小计占该因素下所有水平乳房炎计数总和。[结果]（1）7—9月乳房炎发病次数占比较高。（2）单一乳区感染乳房炎的可能性最大,左前乳区累计发病最多,占比27.7%;其次是右前乳区,占比25.3%。（3）产后14 天内乳房炎发病次数最多,占比10.6%;产后0~105天乳房炎发病次数占比43.2%。（4）奶牛第1次发病后,26.6%牛只会再次发生乳房炎（即复发率超过25%）,而第3次发病占第2次的37.1%。乳房炎发病次数超过5 次及以上时,奶牛乳房炎复发率超过50%。（5）乳房炎治愈天数多集中在0~6天（占比48.9%）和7~13天（占比31.5%）。[结论]为减少奶牛乳房炎频发,需做好7—9月防控,加强产后2周内乳房护理和产后105 天内乳房炎揭发工作,挤奶期间给予前乳区更多观察和护理,及时淘汰乳房炎频发的牛只。

[Objective] By analyzing the incidence of cows’mastitis in 381 large-scale dairy farms in 23 provinces from 2018 to 2022,the aim is to analyze the factors that may affect mastitis：month of onset,position and number of affected udder areas,frequency of onset,days in milk（DIM）,parity,severity,etc..[Method] Multiple cases of different DIM in the same parity of each cow were recorded as multiple. The number of cases was counted and summed according to all cows' mastitis events, and the proportion of each level under different factors was subcounted according to the number of mastitis at each level. [Result] Results showed that：（1）The incidence of mastitis was high in July,August,and September.（2）The risk of infection with mastitis in a single udder area was highest,with the left front udder having the highest cumulative incidence,accounted for 27.7%,followed by the right front udder,accounted for 25.3%.（3）Within 14 days after calving,the highest incidence of mastitis was 10.6%,with 43.2% occurring between 0~105 days after calving.（4）After the first onset,26.6% of cows experienced recurrent mastitis（i.e. a recurrence rate of over 25%）,while the third onset accounted for 37.1% of the second onset. When the incidence of mastitis exceeded five or more times,the recurrence rate of cow mastitis exceeded 50%.（5）The cure days for mastitis were mostly in 0~6 days（48.9%）and 7~13 days（31.5%）.[Conclusion] Therefore,to reduce the frequency of mastitis in dairy cows,it is necessary to do a good job in the prevention and reduce cows’mastitis from July to September,strengthen udder care within 14 days after calving,and detect mastitis within 105 days after calving.More observation and care should be conducted in the front udder when cows in the milking palor,and culling cows with frequent mastitis.