Abstract: By use of a three dimensional air-soil coupling model on M-γ scale, in which the effect of vegetation is considered, some fields of meteorological elements such as temperature, humid and wind, are simulated; further, the weather fire grade in Beijing is calculated.Result shows that the simulated element fields reflect certain specific basic climatic features and variation rules over different surfaces rightly.In addition, the criteria of the weather fire grade are verified reasonable and the simulation of the weather fire grade can show the distribution and intensity of fire danger clearly with high spatial and temporal resolution.The study provides scientific evidences for urban fire monitoring and reduction.