Two severe lightning disasters, which happened on June 24 and July 25, 2007, were compared with lightning location information, circulation backg round, thermal and dynamic characters of ambient field, atmospheric instability and Doppler radar echo feature. Results show that the number of died people of t hunder stroke is relative to the lightning density. These two processes have sim ilar circulation background and synoptic system, but the former has lower sinkin g motion and ascending motion. Both of them are dry in upper air and wet in lowe r, as well as the negative temperature variation in middle atmosphere. Instability index such as CAPE, K index, SI index are all reach the threshold of lightning. The for mer has stronger cold air and higher humidity, as well as the temperat ure inversion in ground layer. The composite reflectivity, echo top heights, ver tical integrated liquid of June 2425 are extremely high for long time, but th e former is obviously larger than the latter. Lightning often happens in the are as of mesoscale convergence system.