Based on nearly 30 year’ observational data and automatic weather station data at different altitudes during 1980-2010, and using weather science theory and mathematical statistics, the precipitation distribution difference and its formation cause between Jiuhua Mountains and its surrounding hills are studied in this paper. The results show that: the spatio temporal distributions of precipitation in different regions are very uneven, and the average annual rainfall in Jiuhua Mountaions is 34.1% more than the surrounding areas, and precipitation mainly is concentrated in May to September. The formation cause mainly exists in the difference between the local water vapor transport conditions and the vertical motion condition in different regions and it affects precipitation when the terrain elevation is higher than 200 m, and rainfall increasing with the increase of altitude, and the enhancement effect on precipitation is the most obvious in 400-900 m height. The terrain effect on rainfall is more significant in mountains, and its average contribution rate is 37.6%. The greater the intensity of precipitation, the more obvious of its effect. Analysis on the differences and the causes of the different regional precipitation distribution offers an important reference to the regional forecasts of rainfall and water resources research applications.