Abstract: [Background] Mycoplasma bovis is a major aetiological agent of bovine respiratory disease complex（BRDC） which causes a variety of respiratory diseases of bovine and results in huge economic losses in livestock farming. Vaccination is the most efficient way to prevent the infections causes by Mycoplasma bovis. [Objective] To understand the pathogenicity of Mycoplasma bovis NM2012 strain by artificial infection tests and to provide potential strains for vaccine development. [Methods] Two-weekold calves were artificially infected by endotracheal inoculation with F_6, F_（12） and F_（20）of Mycoplasma bovis NM2012 strain,respectively. The clinical symptoms of the challenged calves were monitored for consecutive 27 days. At the 14-（th） day postchallenge, 3 calves chosen from each challenged group and 2 calves chosen from control group were killed, respectively. At the 27-（th） day postchallenge, all the other calves were killed. The pathological changes of the killed calves were observed by naked eyes and histologically analyzed. [Results] The F_6,F_（12） and F_（20） of Mycoplasma bovis NM2012 strain exhibited pathogenicity to calves and causes typical symptoms and pathological changes of Mycoplasma bovis pneumonia. [Conclusion] The results suggest that the F_6 to F_（20）of Mycoplasma bovis NM2012 strain remains infectious to bovine, and Mycoplasma bovis NM2012 strain may serve as a candidate strain for vaccine development.