The study of seismogenic structure of earthquake sequence is an important basis for regional seismic activity and seismic risk analysis. In March 2017,an earthquake sequence occurred occurred at the intersection of Tancheng-Lujiang fault zone and Zhangjiakou-Bohai seismic zone in Bohai Sea. The regional structure was relatively complex. It is difficult to deploy instruments in Bohai Sea which make the seismic monitoring capability relatively weak. In this paper,we firstly use the matched filter technique to detect the missing earthquakes in the sequence,and then use the waveform cross-correlation phase detection method to correct the P and S phase arrival time. Based on the corrected phase arrival time data,the sequence is precisely relocated. The focal mechanism of two largest earthquakes in the sequence are calculated. A total of 32 missing earthquakes were detected in the catalog,which is about 1.8 times of the number of earthquakes given in the catalog. According to the waveform cross-correlation clustering analysis,it is found that the Bohai earthquake sequence can be divided into two groups,one is mainshock-aftershock sequence of ML4.4 earthquake,another is earthquake swarm of the largest earthquake ML3.5. Moreover,there is a ML1.6 earthquake that has low similarity with other seismic waveforms,which may be an isolated earthquake event. The results of earthquake relocation and focal mechanism show that the two groups of earthquakes are north-east strikes,the ML4.4 earthquake occurred on the low-dip normal fault,and the ML3.5 earthquake occurred on the high-dip strike-slip fault. Finally,combined with relevant research results of geological structure in the study area,it is considered that seismogenic structure of the ML4.4 aftershock sequence is an extensional normal fault with a north-east low dip angle in Bozhong depression,and the seismogenic structure of the ML3.5 earthquake swarm is a secondary strike-slip fault with a north-east steep dip angle.