The M_S6.6 earthquake in Jinghe on August 9, 2017 and the M_S5.7 earthquake in Kuche on September 16, 2017 occurred successively since August and there were anomalies in the Kümüx seismic window before the two earthquakes. To evaluate the abnormal indicator of the Kümüx seismic window, we investigated the digit seismograph records of the Kümüx seismic station from January 2008 to September 2017, and the monthly frequency change of small earthquakes with M_L ≥ 1.0 and the S-P value of 10s, and defined the monthly frequency of small earthquakes ≥ 54 times(i.e.54 times/month)as the abnormal index of the Kümüx seismic window, as well as their relationship with nearby strong earthquakes. We made an evaluation on its prediction effectiveness by analyzing the abnormal characteristics of the seismic window and the corresponding relation of the moderate strong earthquakes. The main results showed that:(1)The anomaly of the Kümüx seismic window appeared 3.3 and 0.5 months respectively before the M_S6.6 Jinghe earthquake on August 9, 2017 and the M_S5.7 Kuche earthquake on September 16, 2017. (2)There have been 7 groups of anomalies for the Kümüx seismic window since 2008, which were followed by 6 earthquakes of M_S ≥ 5.5 in the central Tianshan area. The advantage time for strong earthquake was within 6 months. (3)The anomaly patterns of monthly frequency for small earthquakes were characterized by high value-low-earthquake or high value-earthquake. The corresponding rate of abnormality was 6/7 and the score of R value was 0.45. The evaluation result of the prediction efficiency for the Kümüx seismic window is better.