X-pattern normal faults developed well in the offshore Bohai Bay basin. On the basis of the interpretation of seismic profiles, the sectional features, formation, controlling mechanisms and its significances on hydrocarbon of the X-pattern normal faults in the offshore Bohai Bay basin were analyzed. The X-pattern normal faults could be divided into incipient and inherited types, including symmetrical and asymmetrical patterns in the seismic sections. The incipient X-pattern normal faults were related with the dextral strike-slipping movement of faults, and developed during the simultaneous slip on the crossing faults. The formation of the inherited X-pattern normal faults was resulted from the preferentially reactivation of the pre-existing basement faults. The X-pattern normal faults had also important influence on the formation of the structural and subtle traps and hydrocarbon migration, as well as the reservoir properties in the study area. The structural and stratigraphic traps related with X-pattern normal faults are the favorable objectives for hydrocarbon exploration in the offshore Bohai Bay basin.