Abstract: The carbon/hydrogen isotope values of single molecule of saturated hydrocarbons has great importance in the judgement of parent material types, evolution degree identification, source rock evaluation and oil-source correlation. Therefore, the sample pre-treatment technique should be given much inportance, particularly for the crude oil and source rocks samples riched in steroids, terpenoids compounds which have experienced the degradation process. A fast and economical methods were established aimed to accurately measuring the carbon/hydrogen isotope values of geological samples by repeated experiments.