Three mirages which took place in 1987 and 2006 were selected and some meteor ological elements during and before the mirage, such as weather situation, surfa ce pressure field, water vapor remotely sensed by GPS and local meteorological f actors were analyzed. The result shows that the mirage usually occurs in the rea r of upper trough. In the meantime, it is in the front of surface high pressure as dry and cold air just passed by. In the coastal region, if there would be the se circumstances, such as a light wind, sharp decrease of temperature , low humi dity, and the dew point deference is not lower than 6℃ at 700hPa, the layer of humid saturated air is in the transient state from an unstable condition to a st able situation of dry air，the wonderful view of mirage would have a high prob ability to take place.