The seismicity of 5°×5° around Jingtai region in Gansu from Jan. 1979 to Sep. 1990 is analysed by means of time space scanning. The blocking segment of seismotectonics of the Jingtai Ms6.2 earthquake on Oct. 20, 1990 is determined. This blocking segment is located in the middle of Menyuan-Haiyuan tectonic belt. The scanning result shows that the earthquakes of Ms≥2.0 occurred mostly on Menyuan-Gulang segment and there are a few on Xiji-Haiyuan segment in that period. The seismicity of these segments echoes each other, and on Xiji-Haiyuan segment the seismicity is delayed for three years. It is possible, that the blocking segment and start time of blocking be found if analysing seismicity by means of time space scanning, and being combined with spatial variation pattern of b value of the seismic risk region for long period.