Abstract: At the end of 2007, Zhejiang Province ADTD (Active Divectory Topology Diagrammer) lightning location network continued to run abnormally. In order to analyze the effect of abnormal operation on lightning location data, this paper selects lightning location data for 2007 and 2008 in Zhejiang Province before and after the system anomaly respectively. And applys the ADTD method to the monthly lightning location data for 2007 and 2008, including the ground-lightning density, the current intensity accumulation percentage and the ADTD location. The results show that there are slightly differences of the groundlightning distribution in individual months and time between 2007 and 2008, but a better agreement for the overall time distribution curve. Also there was no signi ficant difference of the variance of lightning days at the con fidence level of 0.05 and 0.01 between 2007 and 2008. There are several overlapping densities above 6 times / (km²·a) in the high density areas for both of 2007 and 2008. Through general QQplot analysis, the ground-lightning density data sets were close to each other in both 2007 and 2008, so the distribution of ground-lightning density has good consistency. Whether positive or negative ground-lightnings with current intensity less than 50 kA were the vast majority. In the cumulative percentage of current intensity, the value in 2008 was higher than that in 2007. Comparison of location methods, the percentage at four-station location method in 2007 was not so much different from that in 2008, but the percentage at three-station location method in 2007 was above 5.1% higher than that in 2008, it may be considered that the detection accuracy and ef ficiency for 2008 was slightly higher than that in 2007. Although the ADTD abnormal operation at the end of 2007 have a certain impact on the quality of lightning location data, but the differences of overall characteristics are not very obvious between 2007 and 2008.