Based on the monthly precipitation data of Beijing region from 1724 to 2009,this paper calculated the annual statistical characteristics by mathematical statistical methods.The annual mean precipitation is 601.8 mm,with the mean square error is 196.7mm.Also the maximum is 1406mm(1959) and the minimum is 242 mm(1869).The mumber of years of Flood,partial flood,normal,partial drought and drought are 23,28,172,58 and 5a respectively.The correlation coefficient of annual rainfall and rainfall in the four quarter...