In July 2015，25 positive cases of tuberculosis（TB）in a dairy farm were reported from Fengxian district of Shanghai city. Then a field epidemiological investigation in this farm was carried out to find the main causes and the possible risk factors. As a result，the prevalence rate of calves between the ages of 4~6 months was 9.41% and that in the 6~10 month-old cows was 6.25%. The 4 positive sheds were all near the?living?quarters. Among them，the nearest shed to office district was shed No.22，in which the cows were most?susceptible，and the risk of infection was 10.67 times higher than shed No.21（95%CI：3，37.91）. According to the investigation，introduction of animals and flow of people were the main risk factors associated with occurrence of TB in that farm. Some suggestions for preventing the spread of the disease were proposed，including culling all the TB positive cows and conducting bio-safety disposal for dead animals，regularly detecting TB in cows，reducing the flow frequency of people，and thoroughly washing and disinfecting vehicles and instruments when they were in and out of the farm.