Taking the Hohhot-Baotou region（40° ~ 42°N,108°~ 114°E） in Central Inner Mongolia as study area,collecting the earthquake events with ML≥1.0 from January 1,2001 to April 30,2010,the number of seismic samples is sliding scaned and the minimum integrality magnitude Mc is calculated.The Mc change curve with time is drawn also.It is considered that Mc change along with the time is mainly reflected by monitoring capabilities of earthquake station network and seismic activities,but the station layout、the earthquake noise ratio and human factors can also cause short-term or discontinuous Mc change.Meanwhile in two assumptions made by Rydelek,the completeness of earthquake catalog in Hohhot-Baotou area is tested by RS method.The tested result is consistent with our Mc value,and also with the monitoring magnitude range obtained from the monitoring ability of local network.So the study result can truly reflect the integrality of earthquake catalog in Hohhot-Baotou area since 2001.