The evolution of the Gangmar Co-Xiyerkang Dome in the central and western parts of the Qiangtang Basin is analyzed in sedimentary aspects. The dome was primary in the Late Permian, completely developed the Late Triassic-Middle Jurassic and deformed in the Cretaceous-Cenozoic period. Different source-reservoir-cover types developed in the three stages. The half-graben around the dome was better place for oil-gas migration. The strata adjacent to north of the dome were strongly deformed and this was benefit for the preservation of oil and gas.