Abstract: The porosity of source rock is its hydrocarbon generating space.When the pore space of source rock is fully filled by oil,the oil can be discharged effectively from source rock.According to the relationship model of porosity between thermal maturity and density for effective muddy oil source rocks from the Dongying Sag and combined with the relationship between maturity and organic carbon rate of conversion for source rocks of various types,the appraising standard of organic carbon abundance for the effective muddy oil source rocks from the Dongying Sag has been studied.The results show that appraising standard of organic carbon abundance for the effective muddy oil source rocks is great difference.The lowest values of total organic carbon abundance for effective muddy oil source rock with type Ⅰand Ⅱ are 2.01% and 3.51% respectively,and the residual organic carbon abundance for effective muddy oil source rock with typeⅠ and Ⅱ are 0.57% and 2.07% respectively.