Using the earthquake sequence data of MS7.0~7.9 earthquakes since 1966 in mainland China,we study the characteristics of magnitude difference distribution between main shocks and their strong aftershocks and the spatial distribution characteristics of strong aftershocks away from their main shocks.The results show that the magnitude difference distribution obeys intercepted exponential distribution and obtain the B value of 0.72 for the whole earthquake sequences and the B value of 0.73 for the strike-slip earthquake sequences,while the spatial distribution of strong aftershocks obeys normal distribution and the dominated distribution area of strong shocks of strike-slip earthquakes is 5~59 km and 10~29 km for the no-strike-slip earthquakes.