The Nilka-Gongliu earthquake with M_S6.0 and Xinyuan-Hejing earthquake with M_S6. 6 successively occurred in Xinjiang on November 1,2011 and June 30,2012. Massive swarm activity was observed in a large area around the main shock epicenters before the two strong earthquakes. Main features are as follows:(1) The swarm activities not only increased significantly in number of earthquakes,but also presented a distinct swarm gap in spatial distribution,and the epicenters of the following strong earthquakes were all located in the swarm gap.(2) The duration of the swarm gap lasted longer,for 2-3 years.(3) The time-history characteristics of the swarms cumulative frequency indicates that swarm activity was quieter a few months before the main shocks. Finally,we discuss the results as well as the issues of their application in earthquake prediction. The Nilka-Gongliu earthquake with M_S6.0 and Xinyuan-Hejing earthquake with M_S6. 6 occurred occurred in Xinjiang on November 1, 2011 and June 30, 2012. Massive swarm activity was observed in a large area around the main shock epicenters before the two Main features are as follows: (1) The swarm activities not only increased significantly in number of earthquakes, but also presented distinct mass gaps in spatial distribution, and the epicenters of the following strong earthquakes were all located in the swarm gap (2) The duration of the swarm gap lasted longer, for 2-3 years. (3) The time-history characteristics of the swarms cumulative frequency indicates that swarm activity was quieter a few months before the main shocks. Finally, we discuss the results as well as the issues of their application in earthquake prediction.