Abstract: Traditional preparation way of kerogen samples would damage partly the organic matter of source rock,especially marine hydrocarbon source rock which contain organic matter from plankton and animal clastics.This makes it difficult to distinguish organic maceral of the source rock.Taken many experiments,and compared with normal isolation of kerogen and with polished rock slice,the best way of isolation of kerogen is to crash marine hydrocarbon source rock with hammer and then destroy the minerals with non-oxidant acid.The organic matter has been protected perfectly,and is favorable for organic petrology.