3 squall line weather processes in North China were selected and studied, which represent three different types of typical squall line system with trailing stra tiform (TS), leading stratiform (LS) and parallel sratiform (PS). The used data include Doppler radar, cloudtoground lightning, radiosonde and the data by v ariable width netgrids. The relationship between cloudtoground lightning f requency every 6 minutes and echo top parameter was studied by using the top hei ght of whole squall line and its upper part. The results show that cloudtogr ound lightning frequency in period of 6 minutes appeared a range above 8km are 8 5.8%, 78.9% and 80.5%, respectively for three squall processes, and they correla te positively to the areas of cloud tower height reaching above 11km or 12km (ec ho top above 11km). Especially, at part intense lightning activity range of squa ll line systems, the total areas of echo top above 11km can be used as an indica tor of lightning warning. These results are meaningful to the lightning nowcas ting and to understanding of lightning activity in squall line system in North C hina.