The northeastern margin of the Qinghai-Tibetan plateau is an earthquake-prone zone,where some MS≥8.0 strong earthquakes have had serious consequences,for example,the 1920 Haiyuan earthquake of magnitude 8.5 resulted in more than 220 000 deaths.The Minxian-Zhangxian MS6.6 earthquake of 2013,which occurred in the northeastern margin of the Qinghai-Tibetan plateau,broke about ten years of seismic quiescence （MS≥6.0） since the Minle earthquake of 2003.The significance of the MS6.6 earthquake and the earthquake tendency has attracted a great deal of attention,because many seismologists believe that the seismic risk in this area increased after the Wenchuan earthquake of 2008.The Benioff strain energy is a physical quantity that can be used to describe seismic activity,and it contains information on the frequency and strength of earthquakes in a given region.Some research on Benioff strain energy has been done to obtain a law for seismic activity.In this article,we calculate the Benioff strain energy of MS≥6.0 earthquakes in the northeastern margin of the Qinghai-Tibetan plateau,and analyze the periodic characteristics of MS≥6.0 strong earthquakes from 1875 to 2013 using the Morlet wavelet method.The results show that there were several main periods of activity,which are about 2 to 3 years,8 to 10 years,and 25 to 30 years,and the first two periods were determined after the significance test was made,From the Benioff strain energy,the frequency of strong earthquakes in the northeastern margin of the Qinghai-Tibetan plateau has been normal since 1977,but the strength is relatively low.Using the effective earthquake case,this paper also discusses the background of the Minxian-Zhangxian MS6.6 earthquake and estimates the postearthquake trend by analyzing the relationship between the probability of earthquake occurrence and the leaving time.The results show that there is a fairly large risk of a MS ≥ 7.0 earthquake in this region.The probability of earthquake occurrence has significantly increased since the Gonghe MS7.0 earthquake of 1990,and it will reach 1.00 by the end of 2015.In summary,the Minxian-Zhangxian MS6.6 earthquake displays the risk of a strong earthquake in the northeastern margin of the QinghaiTibetan plateau and may be an inflection point for the strength of seismic activity in this region.The primary results in this paper have a reference value for seismic research.