Abstract: The fluid inclusions of Jurassic reservoir in Yanqi basin Northwest China mainly distributed in Sangonghe Formation and Badaowan Formation, its homogeneous temperature mostly was 101-110℃ and 121-130℃. The N-alkane carbon atomic numbers assumed two kurtosis in its inclusion component, the first main peak carbon was nC₁₈ or nC₂₀, the following main peak carbon was nC₂₆ or nC₂₇, these characteristics instructed that the basin occurred two oilgas accumulation phases during the midlate Jurassic; But the autogenetic illite isotope dating in its reservoir instructed similarly two oil-gas accumulation phase in the north depression of the Bohu sag, namely the MidLate Jurassic (142.26-183.15 Ma) and the Late Cretaceous (75.07-142.26 Ma)，thereinto the oil-gas accumulation phases in the south topographic depression and the Benbutu structure belt respectively were the Mid Jurassic and the Mid-Late Jurassic-Early Cretaceous, the K-Ar dating increased with its burying depth in the identical structure belt on the longitudinal, which reflected that the oil-gas injected, migrated and adju sted gradually from the low structure spot to the high structure spot.

Key words: Yanqi basin, fluid inclusion, homogeneous temperature, autogenetic illite, isotope-dating, oil-gas accumulation phases