Abstract The light hydrocarbon data from 772 oil samples in 25 oilfields, together with GC/MS data from 338 saturated hydrocarbon samples were used to discuss the relationship between kerogen types, using the heptane value, isoheptane value and C 29 sterane 20 S/( S+ R) ratio. Although the heptane and isoheptane values are related to kerogen type, the correlation is different from that in Thompson's interpretation, so the correlation cannot be directly used in research on land facies oils in China. Consideration should be taken when using the heptane and isoheptane values, as secondary alteration and mixed oil sources are the main factors leading to the abnormal change in heptane and isoheptane values. The heptane and isoheptane values have a larger maturity range than that of C 29 sterane 20S/(S+R). There are three types of oil samples (original immature oil, altered oil and mixed source oil with different maturity) that may fall into the “Biodegradation” area of the Thompson interpretation. For the biodegraded oil in Thompson's interpretation, the reservoir may have undergone a secondary charge.