Abstract: Through the research on the reservoir-forming conditions of complex fault-block oil reservoirs in Jizhong Depression, the results show that its reservoir-forming condition is relatively good. Themain factors that control the formation of oil reservoirs include structural setting, sealing feature of fault, oil-generation combinations, and sand body types etc. The reservoir-forming patterns include anticlinal type, sloping type, and multiple faulted type etc. But the large differences in control factors, enrichment degree and reservoir distribution each among these reservoir-forming patterns, therefore, much attention should be paid in the exploration of complex faultblock oil reservoirs.