Based on the NCEPNCAR data and the observational data on March 910, 2006, a diagnostic analysis is conducted for the development of Mongolia cyclone inducing the severe dust storm. The results show that highlevel anticyclonic flows contribute to development of the wave energy, and make the explosive cyclon e. Although vorticity advection and thermal advection are important to the cyclo ne development, vorticity advection is weaker than thermal advection at the firs t stage of cyclone development. The baroclinicity in the lower troposphere stren gthens significantly with frontolysis at the rear part of the cyclone and the fr ontogenesis of foreside the cyclone, which is helpful for release of available p otential energy, production of kinetic energy and the development of the cyclone . In addition, the potential vorticity analysis indicates that the cyclone devel opment is related to the activities of cold air, and there exist distinct intera ctions between systems of the upper and lower troposphere, but the role of water vapour and release of potential heat is not obvious. The mechanism of developme nt of cyclone is quite different from that of other cyclones associated with the summer precipitation in China.