Abstract: There are large areas being of thick coal beds in Huimin Sag,but there are no uniform and effective standards for the potential evaluation of gas generation.In this article the concept of effective gas source rock is outlined,the maximum gas adsorption volume of caol beds is determined by experiments,the lower limits of gas generation potential of coal beds are put out and their available application scope are point out under different evolution stages combined with the relationship of gas generation rate and indicators (such as S ₁+S ₂,HI and R _max) in thermal simulation experiment.The gas generation potential of coal beds is evaluated according to these standards,this confirms an idea that the coal beds in this area can act as effective gas source rocks.This work will push on the exploration of coal soured gas in this area and will be valuable referencs for the coal soured gas exploration in other parts of Bohai Gulf Basin.