Abstract: As a new developed method for estimating earthquake detection probabilities, the probability-based magnitude of completeness (PMC) method can avoid decreasing the detection capability resulted by artificial factors, and can access the detection capability in the areas where traditional Gutenberg-Richter relationship-based method is ineffective due to lack of earthquakes. In this study, we determine the detection probability of all 39 stations of the Inner Mongolia seismic network by using the PMC method. The results show that the PMC method can reflect the network earthquake monitoring capacity objectively. The detection probability is better than other regions in the midwestern and the mid-eastern region of Inner Mongolia, due to better coverage of seismic stations, however, it is poor in the Alxa Youqi region, the Sino-Russian border, and Sino-Mongolia border. Synthesized detection probability results indicate that minimum probability-based magnitude of completeness, M_P, can reach M_L2.2 in the 80% area of the Inner Mongolia when the stations of the neighboring networks are involved, and only about M_L3.3 in other areas. In order to enhance the monitoring capacity of Inner Mongolia regional seismic network, more stations are still needed to emplace in the Sino-Mongolia border region, the northeastern region of Inner Mongolia, and to the west of Alxa Zuoqi to optimize the layout of seismic network.