Based on core observation, this paper analyzed the petrology characteristics and primary sedimentary structure and other sedimentary facies symbols, and concluded that the gravity current sedimentation of Chang 6 oil reservoir set in Huachi area is mainly consist of sandy debris flow and turbidity current sedimentation. These two kinds of gravity current sedimentation stay quite different in their growing location. Sandy debris flow locates in upstream, while turbidity current sedimentation stays in downstairs. This difference leads to the zonation in reservoir characteristics between south and north. Sandy debris flow has lower compositional maturity and interstitial fillings but better reservoir physical properties and oiliness, while turbidity current sandstone reservoir performs by contraries. The types of interstitial fillings of reservoir sand body of Chang 6 oil reservoir set in Huachi area are mostly illite, calcareous cementitious and chlorite film. Sandy debris flow has higher contents of illite and calcareous cementitious, but turbidity sand body possesses higher contents of chlorite film. The main reservoir space of Chang 6 oil reservoir set in Huachi area is primary intergranular pores and intragranular dissolved pores. The surface porosity of sandy debris flood is apparently higher than that of turbidity sand body. The feldspar which consists more sandy debris flood provides more physical foundation of dissolution, thus the content of intragranular dissolved pores in sandy debris flow sand body is larger than that of turbidity sand body.