A microburst process on 12 July 2017 near Ningbo Airport is simulated by the mesoscale numerical model WRFV3.6 and its formation mechanism is analyzed using the data of automatic meteorological stations over Zhejiang Province, automatic observation data collected at the airport and Doppler radar data. The study shows that the microburst was triggered by a strong thunderstorm which was caused by a sea breeze front. The changes of wind, temperature, pressure of the AWOS observation data show the obvious characteristics of microburst. The horizontal wind field structure of the microburst is simulated well in the simulation test. Dragging effect, hail melting during subsidence, continuous evaporation, and cooling of liquid water and rainwater are important reasons for the formation of the microburst. Lowlevel temperature disturbance enhanced vertical motion, and the abnormal increase area of the middle and lowlevel vortex has a good correspondence with the thunderstorm heavy rainfall area.