The ground precipitation is divided into 3 intervals (10 to 25, 25 to 50, and 50 to 100 mm/h), and with the hourly precipitation measurements from weather radar and national surface observation automatic weather stations from ASOM from May to October in 2010, using three time standard deviation method, the threshold parameters of precipitation observation differences for two kind of equipment are determined month by month, and a real time rainfall calibration technique between weather radar and automatic weather stations is devised. Using this method, the accuracy of rainfall between May and October 2011 is tested. The results show that the correct rate of the rainfall is greater than 85% after using this new method, which means that this method is effectible in testing the surface precipitation measurements from automatic weather stations in real time.