Horinger of Inner Mongolia is located in the Yinshan seismic zone on the northern margin of the Ordos block,and in which strong earthquakes of magnitude 6 or above are frequent in history. A M_L4.5 earthquake in Horinger on March 30,2020 broke the long quiescence of earthquakes above M_L4.0 in the Yinshan seismic zone since 2005. The analysis of the seismogenic structure of the 2020 Horinger earthquake sequence is of great importance to the regional stress and seismic risk research. However,the stations around Horinger are sparse and earthquake monitoring capacity are relatively weak in comparison to other areas in North China,which has a negative impact on the analysis of the Horinger 2020 earthquake sequence. In this paper,we used Match and Locate method(M&L)to detect the micro-earthquakes missed in network catalog,relocated the earthquakes detected,and used Cut and Paste method(CAP)to calculate the mechanism of M_L4.5 earthquake. Using M&L we detected a total of 61 locatable earthquake events,which is about 1.3 times as much as that in the network catalog,and the number of locatable earthquakes is about 2.9 times as much as that in the network catalog. The relocation result shows that the epicenters of earthquake sequence are in NE direction distribution,which is basically consistent with the north-east plane of M_L4.5 earthquake mechanism obtained by CAP method. Considered the relocation result and source mechanism,the seismogenic structure of the 2020 Horinger earthquake sequence is a normal fault in NE strike direction and NW dip direction. Combined with regional seismic geological structure characteristics,we conclude that the seismogenic structure of the M_L4.5 earthquake sequence is the south margin fault of Daihai-Huangqihai Basin.