Abstract: Downburst is a very dangerous weather phenomenon for aeroplane flying in or flying off the airport. In order to understand the initial formation and evolution of downburst and to study the effects of atmospheric environment condition and the microstructure of cloud-precipitation particles on the downburst development processes, we have designed and carryed out a modeling scheme by use of our own unhydrostatic compressible mesoscale-γ model including necessary cloud-precipitation processes. The initial condition of temperature, humidity and wind is from aobservation case on which the downburst occurred. The results of tomputations demonstrated the evolution of downburst and showed the variation of various environmental and microphysical parameters. Some of the mechanism about the downburst occurrence have been obtained. All the statements may be help the forecastor working in airport to manage the occurrence of downburst better.