Abstract: Effected by regional tectonic stress field, Xihu Sag has undergone rifting, sinking and regional subsidence phases. Baochu slope is a sub-structure union, it developed two group of faults different size and different kind according to the different evolvement time, giving priority to the NE- NEE and NW direction. Being observed from the top, all the faults had clear orientation and subsection of SN, and had clear beds in the vertical. The faults were the channels of oil & gas in the vertical and lateral direction, but also may be the barrier of movement of oil & gas. The faults also had effected the local structures in Baochu slope, including the types of traps and their forming phases controlled the vertical superposed mode of oil & gas. The tectonic transport controlled the lateral distribution of oil & gas. Now there were four petroliferous structures such as Pinghu, Baoyunting, Wuyunting and Kunqueting.