Abstract: The Huanghua depression is a Meso-Cenozoic basin.On the basis of geological and geochemical data,the threshold values proposed for oil generation in the basin is 2,200 meters for depth and 90℃ for temperature,and for oil and gas maturation and expulsion 2,600 meters and 101℃.Four stages are presented for evolution of oil and gas.immature stage,sub-mature stage,mature stage and supermature stage.The defines of "liquid state window" is preliminarily established.Based on the relationship of changes of mudstone porosity,hydrocarbon conversion ratio and hydrocarbon expulsion curves with increasing depth,the author has analysed the process of primary migration and pointed out that primary migration of oil and gas in this area occurred when the source rocks were buried at 2,600-3,400 meters.Predictions are made also for other areas with conditions unknown.