Based on the circulation patterns in the upper air and at surface, C band Doppler radar products such as reflectivity factor and radar velocity, and automatic station data in Datong, the large area precipitation process on 29 July 2011 is analyzed. The operational conditions for weather modification operation are investigated based on automatic station data. The effect of the weather modification operation is examined scientifically through radar tracking and observing, radar echo animation demonstration, echo strength comparison before and after the operation, and comparison between operation spot and non operation spot, combined with automatic weather station data.The results show that there is certain correlation between the large area continuous precipitation and artificial precipitation enhancement operation.